Hydrogen-producing fuel processing assemblies, heating assemblies, and methods of operating the same

ABSTRACT

Combustion-based heating assemblies and hydrogen-producing fuel processing assemblies that include at least a reforming region adapted to be heated by the heating assemblies. The heating assembly may include at least one fuel chamber and at least one heating and ignition source. The at least one fuel chamber may be adapted to receive at least one fuel stream at a first temperature. The fuel stream may include a liquid, combustible, carbon-containing fuel having an ignition temperature greater than the first temperature at which the fuel stream is delivered to the fuel chamber. The at least one heating and ignition source may be adapted to heat at least a portion of the fuel chamber to raise the temperature of at least a portion of the carbon-containing fuel to a second temperature at least as great as the ignition temperature and to ignite the carbon-containing fuel. Methods of use are also disclosed.

RELATED APPLICATIONS

This application is a divisional patent application of and claimspriority to U.S. patent application Ser. No. 11/226,810, which was filedon Sep. 13, 2005, issued on Dec. 15, 2009 as U.S. Pat. No. 7,632,322,and claims priority to Provisional Patent Application Ser. No.60/688,430, which was filed on Jun. 7, 2005. The complete disclosures ofthe above patent applications are hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure is directed generally to hydrogen-producing fuelprocessing systems, and more particularly, to combustion-based heatingassemblies for use in such fuel processing systems.

BACKGROUND OF THE DISCLOSURE

Purified hydrogen is used in the manufacture of many products includingmetals, edible fats and oils, and semiconductors and microelectronics.Purified hydrogen is also an important fuel source for many energyconversion devices. For example, many fuel cells use purified hydrogenand an oxidant to produce an electrical potential. A series ofinterconnected fuel cells is referred to as a fuel cell stack, and thisstack may be referred to as a fuel cell system when combined withsources of oxidant and hydrogen gas. Various processes and devices maybe used to produce the hydrogen gas that is consumed by the fuel cells.

As used herein, a fuel processing assembly is a device or combination ofdevices that produces hydrogen gas from one or more feed streams thatinclude one or more feedstocks. Examples of fuel processing assembliesinclude steam and autothermal reformers, in which the feed streamcontains water and a carbon-containing feedstock, such as an alcohol ora hydrocarbon, and partial oxidation and pyrolysis reactors, in whichthe feed stream is a carbon-containing feedstock. Fuel processorstypically operate at elevated temperatures. In endothermic fuelprocessing reactions, such as in steam reforming fuel processingassemblies, the heat required to heat the fuel processing assembly needsto be provided by a heating assembly, such as a burner, electricalheater or the like. When burners are used to heat the fuel processor,the burners typically utilize a combustible fuel stream, such as acombustible gas or a combustible liquid.

One such hydrogen-producing fuel processing assembly includes a steamreformer, in which hydrogen gas is produced from a feed stream thatincludes a carbon-containing feedstock and water. Steam reforming isperformed at elevated temperatures and pressures, and a steam reformertypically includes a heating assembly that provides heat for the steamreforming reaction. Illustrative but not exclusive uses of the heatinclude maintaining the reforming catalyst bed at a selected reformingtemperature, or temperature range, and vaporizing a liquid feed streamprior to its use to produce hydrogen gas. One type of heating assemblyis a burner, in which a combustible fuel stream is combusted with air.Additionally, steam reforming fuel processing assemblies conventionallyutilize a fuel stream that has a different composition than the feedstream and which is delivered to, and consumed by, the burner or otherheating assembly to heat the steam reformer and/or the feed stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a fuel processing assembly with aheating assembly according to the present disclosure.

FIG. 2 is a schematic diagram of a fuel cell system with a heatingassembly according to the present disclosure.

FIG. 3 is a schematic diagram of another fuel processing assembly with aheating assembly according to the present disclosure.

FIG. 4 is a schematic view of a fuel processing assembly according tothe present disclosure in which the hydrogen-producing region and theheating assembly both receive the same liquid carbon-containingfeedstock.

FIG. 5 is a schematic view showing a variation of the fuel processingassembly of FIG. 4, with a carbon-containing feedstock being deliveredto the hydrogen-producing region and the burner assembly from the samesupply stream.

FIG. 6 is a schematic view of a fuel processing assembly according tothe present disclosure in which the hydrogen-producing region and theburner assembly both receive fuel, or feed, streams containing water anda liquid carbon-containing feedstock.

FIG. 7 is a schematic view showing a variation of the fuel processingassembly of FIG. 6, with the hydrogen-producing region and the burnerassembly both receiving fuel, or feed, streams containing water and acarbon-containing feedstock from the same supply stream.

FIG. 8 is a schematic view showing another variation of the fuelprocessing assemblies of FIGS. 6 and 7.

FIG. 9 is a schematic view of another example of a fuel processingassembly according to the present disclosure.

FIG. 10 is a schematic view of a heating assembly according to thepresent disclosure.

FIG. 11 is a graph illustrating the relationship between the flash pointof a methanol-water solution and the weight percentage of methanol insolution.

FIG. 12 is another schematic view of a fuel processing assemblyincluding a partial cut-away view of a heating assembly according to thepresent disclosure.

FIG. 13 is another schematic view of a heating assembly according to thepresent disclosure.

FIG. 14 is a more detailed schematic view of a fuel processing assemblyincluding a partial cut-away view of a heating assembly according to thepresent disclosure.

FIG. 15 is a partial cross-sectional view of the fuel processingassembly of FIG. 14 showing a heating assembly according to the presentdisclosure in cross-section.

FIG. 16 is a cross-sectional view of another heating assembly accordingto the present disclosure and showing primary and start-up burnerassemblies.

FIG. 17 is a cross-sectional view of another heating assembly accordingto the present disclosure.

FIG. 18 is a side elevation view of another fuel processing assemblywith a heating assembly according to the present disclosure.

FIG. 19 is a partial cross-sectional end view of the fuel processingassembly of FIG. 18.

FIG. 20 is a schematic diagram of a steam reformer having a heatingassembly according to the present disclosure and being in communicationwith a fuel cell stack.

DETAILED DESCRIPTION AND BEST MODE OF THE DISCLOSURE

The present disclosure is directed to hydrogen-producing fuel processingassemblies, such as may be used in fuel cell systems, and moreparticularly, to fuel processing assemblies that include heatingassemblies adapted to receive and combust a liquid fuel stream to heatat least the hydrogen-producing region of the fuel processing assembly.The hydrogen-producing region includes a suitable catalyst to utilize asteam reforming, or other endothermic, reaction to produce hydrogen gas.The hydrogen-producing region is adapted to receive at least one feedstream, which individually or collectively comprise a carbon-containingfeedstock and water, to produce an output stream comprising hydrogen gasas a majority component. The fuel processing assembly is in thermalcommunication with a combustion-based heating assembly that is adaptedto receive, ignite and combust a fuel stream to produce a heatedcombustion stream for heating at least the hydrogen-producing region.The heating assembly may include at least one fuel chamber and at leastone heating and ignition source. In some embodiments, the fuel chambermay be adapted to receive at least one fuel stream comprising liquid,combustible, carbon-containing fuel, and may be adapted to receive apredetermined volume of combustible, carbon-containing fuel via the atleast one fuel stream. In some embodiments, the fuel includes methanolor another alcohol, and in some embodiments the fuel further includeswater. In some embodiments, the feed stream and the fuel stream eachcomprise at least one common carbon-containing component, and in someembodiments the feed stream and the fuel stream have the samecomposition and/or are drawn from a common source. In some embodiments,the fuel chamber may include a liquid fuel region and a fuel vaporregion. The at least one heating and ignition source may be disposed atleast partially in the fuel vapor region. In some embodiments, theheating and ignition source may be disposed between the liquid fuelregion and the reforming region. Additionally or alternatively, the fuelchamber may include an at least substantially open reservoir, which, insome embodiments, may include a transport medium adapted to promotedelivery of the liquid fuel to the fuel vapor region.

The fuel stream may enter the fuel chamber at a first temperature andmay have an ignition temperature greater than the first temperature. Insome embodiments, the carbon-containing fuel delivered to the fuelchamber may have an ignition partial pressure, and the carbon-containingfuel in the fuel chamber may have an initial partial pressure less thanits ignition partial pressure. As used herein, “ignition temperature”refers to the minimum temperature at which ignition of the fuel streamwill occur in the presence of sufficient air to support combustion. Asused herein, “ignition vapor pressure” refers to the minimum vaporpressure at which ignition of the fuel stream in air will occur.

In some embodiments, the at least one heating and ignition source may beadapted to heat at least a portion of the fuel chamber to raise thetemperature of at least a portion of the carbon-containing fuel to asecond temperature that is at least as great as the ignition temperatureand to ignite the carbon-containing fuel. Additionally or alternatively,the heating and ignition source may be adapted to heat at least aportion of the fuel chamber to raise the partial pressure of thecarbon-containing fuel in at least a portion of the fuel vapor region ofthe fuel chamber to a second partial pressure at least as great as theignition partial pressure and may be adapted to ignite at least aportion of the fuel. In some embodiments, the at least one heating andignition source may comprise an electrical resistance heating elementadapted to be heated to a heating element ignition temperature at whichthe heating element is adapted to ignite the carbon-containing fuel inthe fuel chamber.

A fuel processing assembly is shown in FIG. 1 and is indicated generallyat 10. Fuel processing assembly 10 includes a fuel processor 12 that isadapted to produce a product hydrogen stream 14 containing hydrogen gas,and preferably at least substantially pure hydrogen gas, from one ormore feed streams 16. Feed stream 16 may include at least onecarbon-containing feedstock 18. Fuel processor 12 is any suitabledevice, or combination of devices, that is adapted to produce hydrogengas from feed stream(s) 16. Accordingly, fuel processor 12 includes ahydrogen-producing region 19, in which an output stream 20 containinghydrogen gas is produced by utilizing any suitable hydrogen-producingmechanism(s). Output stream 20 includes hydrogen gas as at least amajority component. Output stream 20 may include one or more additionalgaseous components, and thereby may be referred to as a mixed gas streamthat contains hydrogen gas as its majority component.

Examples of suitable mechanisms for producing hydrogen gas from feedstream(s) 16 include steam reforming and autothermal reforming, in whichreforming catalysts are used to produce hydrogen gas from a feed stream16 containing a carbon-containing feedstock 18 and water 17. Othersuitable mechanisms for producing hydrogen gas include pyrolysis andcatalytic partial oxidation of a carbon-containing feedstock, in whichcase the feed stream does not contain water. Still another suitablemechanism for producing hydrogen gas is electrolysis, in which case thefeedstock is water. Examples of suitable carbon-containing feedstocks 18include at least one hydrocarbon or alcohol. Examples of suitablehydrocarbons include methane, propane, natural gas, diesel, kerosene,gasoline and the like. Examples of suitable alcohols include methanol,ethanol, and polyols, such as ethylene glycol and propylene glycol.

Feed stream(s) 16 may be delivered to fuel processor 12 via any suitablemechanism. While a single feed stream 16 is shown in FIG. 1, it iswithin the scope of the disclosure that more than one stream 16 may beused and that these streams may contain the same or differentfeedstocks. This is schematically illustrated by the inclusion of asecond feed stream 16 in dashed lines in FIG. 1. When feed stream 16contains two or more components, such as a carbon-containing feedstockand water, the components may be delivered in the same or different feedstreams. For example, when the fuel processor is adapted to producehydrogen gas from a carbon-containing feedstock and water, thesecomponents are typically delivered in separate streams, and optionally(at least until both streams are vaporized or otherwise gaseous), whenthey are not miscible with each other, such as shown in FIG. 1 byreference numerals 17 and 18 pointing to different feed streams. Whenthe carbon-containing feedstock is miscible with water, the feedstock istypically, but is not required to be, delivered with the water componentof feed stream 16, such as shown in FIG. 1 by reference numerals 17 and18 pointing to the same feed stream 16. For example, when the fuelprocessor receives a feed stream containing water and a water-solublealcohol, such as methanol, these components may be premixed anddelivered as a single stream.

In FIG. 1, feed stream 16 is shown being delivered to fuel processor 12by a feedstock delivery system 22, which schematically represents anysuitable mechanism, device or combination thereof for selectivelydelivering the feed stream to the fuel processor. For example, thedelivery system may include one or more pumps that are adapted todeliver the components of stream 16 from one or more supplies.Additionally, or alternatively, feedstock delivery system 22 may includea valve assembly adapted to regulate the flow of the components from apressurized supply. The supplies may be located external of the fuelprocessing assembly, or may be contained within or adjacent theassembly. When feed stream 16 is delivered to the fuel processor in morethan one stream, the streams may be delivered by the same or separatefeedstock delivery systems.

Steam reforming is one example of a hydrogen-producing mechanism thatmay be employed in hydrogen-producing region 19 in which feed stream 16comprises water and a carbon-containing feedstock. In a steam reformingprocess, hydrogen-producing region 19 contains a suitable steamreforming catalyst 23, as indicated in dashed lines in FIG. 1. In suchan embodiment, the fuel processor may be referred to as a steamreformer, hydrogen-producing region 19 may be referred to as a reformingregion, and output, or mixed gas, stream 20 may be referred to as areformate stream. As used herein, reforming region 19 refers to anyhydrogen-producing region utilizing a steam reforming hydrogen-producingmechanism. Examples of suitable steam reforming catalysts includecopper-zinc formulations of low temperature shift catalysts and achromium formulation sold under the trade name KMA by Stid-Chemie,although others may be used. The other gases that are typically presentin the reformate stream include carbon monoxide, carbon dioxide,methane, steam, and/or unreacted carbon-containing feedstock.

As an illustrative example of temperatures that may be achieved and/ormaintained in hydrogen-producing region 19 through the use of heatingassembly 60, hydrogen-producing steam reformers typically operate attemperatures in the range of 200° C. and 900° C. Temperatures outside ofthis range are within the scope of the disclosure. When thecarbon-containing feedstock is methanol, the steam reforming reactionwill typically operate in a temperature range of approximately 200-500°C. Illustrative subsets of this range include 350-450° C., 375-425° C.,and 375-400° C. When the carbon-containing feedstock is a hydrocarbon,ethanol, or a similar alcohol, a temperature range of approximately400-900° C. will typically be used for the steam reforming reaction.Illustrative subsets of this range include 750-850° C., 725-825° C.,650-750° C., 700-800° C., 700-900° C., 500-800° C., 400-600° C., and600-800° C. It is within the scope of the present disclosure for thehydrogen-producing region to include two or more zones, or portions,each of which may be operated at the same or at different temperatures.For example, when the hydrogen-production fluid includes a hydrocarbon,in some embodiments it may be desirable to include two differenthydrogen-producing portions, with one operating at a lower temperaturethan the other to provide a pre-reforming region. In such an embodiment,the fuel processing system may alternatively be described as includingtwo or more hydrogen producing regions.

In many applications, it is desirable for the fuel processor to produceat least substantially pure hydrogen gas. Accordingly, the fuelprocessor may utilize a process that inherently produces sufficientlypure hydrogen gas. When the output stream contains sufficiently purehydrogen gas and/or sufficiently low concentrations of one or morenon-hydrogen components for a particular application, product hydrogenstream 14 may be formed directly from output stream 20. However, in manyhydrogen-producing processes, output stream 20 will be a mixed gasstream that contains hydrogen gas as a majority component along withother gases. Similarly, in many applications, the output stream 20 maybe substantially pure hydrogen but still contain concentrations of oneor more non-hydrogen components that are harmful or otherwiseundesirable in the application for which the product hydrogen stream isintended to be used.

Fuel processing assembly 10 may (but is not required to) further includea purification region 24, in which a hydrogen-rich stream 26 is producedfrom the output, or mixed gas, stream. Hydrogen-rich stream 26 containsat least one of a greater hydrogen concentration than output stream 20and a reduced concentration of one or more of the other gases orimpurities that were present in the output stream. Purification region24 is schematically illustrated in FIG. 1, where output stream 20 isshown being delivered to an optional purification region 24. As shown inFIG. 1, at least a portion of hydrogen-rich stream 26 forms producthydrogen stream 14. Accordingly, hydrogen-rich stream 26 and producthydrogen stream 14 may be the same stream and have the same compositionsand flow rates. However, it is also within the scope of the presentdisclosure that some of the purified hydrogen gas in hydrogen-richstream 26 may be stored for later use, such as in a suitable hydrogenstorage assembly, and/or consumed by the fuel processing assembly.

Purification region 24 may, but is not required to, produce at least onebyproduct stream 28. When present, byproduct stream 28 may be exhausted,sent to a burner assembly or other combustion source, used as a heatedfluid stream, stored for later use, or otherwise utilized, stored ordisposed of. It is within the scope of the disclosure that byproductstream 28 may be emitted from the purification region as a continuousstream responsive to the delivery of output stream 20 to thepurification region, or intermittently, such as in a batch process orwhen the byproduct portion of the output stream is retained at leasttemporarily in the purification region.

Purification region 24 includes any suitable device, or combination ofdevices, that are adapted to reduce the concentration of at least onecomponent of output stream 20. In most applications, hydrogen-richstream 26 will have a greater hydrogen concentration than output, ormixed gas, stream 20. However, it is also within the scope of thedisclosure that the hydrogen-rich stream will have a reducedconcentration of one or more non-hydrogen components that were presentin output stream 20, yet have the same, or even a reduced overallhydrogen concentration as the output stream. For example, in someapplications where product hydrogen stream 14 may be used, certainimpurities, or non-hydrogen components, are more harmful than others. Asa specific example, in conventional fuel cell systems, carbon monoxidemay damage a fuel cell stack if it is present in even a few parts permillion, while other non-hydrogen components that may be present instream 20, such as water, will not damage the stack even if present inmuch greater concentrations. Therefore, in such an application, asuitable purification region may not increase the overall hydrogenconcentration, but it will reduce the concentration of a non-hydrogencomponent that is harmful, or potentially harmful, to the desiredapplication for the product hydrogen stream.

Illustrative examples of suitable devices for purification region 24include one or more hydrogen-selective membranes 30, chemical carbonmonoxide removal assemblies 32, and pressure swing adsorption systems38. It is within the scope of the disclosure that purification region 24may include more than one type of purification device, and that thesedevices may have the same or different structures and/or operate by thesame or different mechanisms.

Hydrogen-selective membranes 30 are permeable to hydrogen gas, but areat least substantially, if not completely, impermeable to othercomponents of output stream 20. Membranes 30 may be formed of anyhydrogen-permeable material suitable for use in the operatingenvironment and parameters in which purification region 24 is operated.Examples of suitable materials for membranes 30 include palladium andpalladium alloys, and especially thin films of such metals and metalalloys. Palladium alloys have proven particularly effective, especiallypalladium with 35 wt % to 45 wt % copper. A palladium-copper alloy thatcontains approximately 40 wt % copper has proven particularly effective,although other relative concentrations and components may be used withinthe scope of the disclosure.

Hydrogen-selective membranes are typically formed from a thin foil thatis approximately 0.001 inches thick. It is within the scope of thepresent disclosure, however, that the membranes may be formed from otherhydrogen-permeable and/or hydrogen-selective materials, including metalsand metal alloys other than those discussed above as well asnon-metallic materials and compositions, and that the membranes may havethicknesses that are greater or less than discussed above. For example,the membrane may be made thinner, with commensurate increase in hydrogenflux. Examples of suitable mechanisms for reducing the thickness of themembranes include rolling, sputtering and etching. A suitable etchingprocess is disclosed in U.S. Pat. No. 6,152,995, the complete disclosureof which is hereby incorporated by reference for all purposes. Examplesof various membranes, membrane configurations, and methods for preparingthe same are disclosed in U.S. Pat. Nos. 6,221,117, 6,319,306, and6,537,352, the complete disclosures of which are hereby incorporated byreference for all purposes.

Chemical carbon monoxide removal assemblies 32 are devices thatchemically react carbon monoxide and/or other undesirable components ofstream 20, if present in output stream 20, to form other compositionsthat are not as potentially harmful. Examples of chemical carbonmonoxide removal assemblies include water-gas shift reactors and otherdevices that convert carbon monoxide to carbon dioxide, and methanationcatalyst beds that convert carbon monoxide and hydrogen to methane andwater. It is within the scope of the disclosure that fuel processingassembly 10 may include more than one type and/or number of chemicalremoval assemblies 32.

Pressure swing adsorption (PSA) is a chemical process in which gaseousimpurities are removed from output stream 20 based on the principle thatcertain gases, under the proper conditions of temperature and pressure,will be adsorbed onto an adsorbent material more strongly than othergases. Typically, it is the impurities that are adsorbed and removedfrom output stream 20. The success of using PSA for hydrogenpurification is due to the relatively strong adsorption of commonimpurity gases (such as CO, CO₂, hydrocarbons including CH₄, and N₂) onthe adsorbent material. Hydrogen adsorbs only very weakly and sohydrogen passes through the adsorbent bed while the impurities areretained on the adsorbent material. Impurity gases such as NH₃, H₂S, andH₂O adsorb very strongly on the adsorbent material and are removed fromstream 20 along with other impurities. If the adsorbent material isgoing to be regenerated and these impurities are present in stream 20,purification region 24 preferably includes a suitable device that isadapted to remove these impurities prior to delivery of stream 20 to theadsorbent material because it is more difficult to desorb theseimpurities.

Adsorption of impurity gases occurs at elevated pressure. When thepressure is reduced, the impurities are desorbed from the adsorbentmaterial, thus regenerating the adsorbent material. Typically, PSA is acyclic process and requires at least two beds for continuous (as opposedto batch) operation. Examples of suitable adsorbent materials that maybe used in adsorbent beds are activated carbon and zeolites, especially5 Å (5 angstrom) zeolites. The adsorbent material is commonly in theform of pellets and it is placed in a cylindrical pressure vesselutilizing a conventional packed-bed configuration. Other suitableadsorbent material compositions, forms, and configurations may be used.

PSA system 38 also provides an example of a device for use inpurification region 24 in which the byproducts, or removed components,are not directly exhausted from the region as a gas stream concurrentlywith the purification of the output stream. Instead, these byproductcomponents are removed when the adsorbent material is regenerated orotherwise removed from the purification region.

In FIG. 1, purification region 24 is shown within fuel processor 12. Itis within the scope of the disclosure that region 24, when present, mayalternatively be separately located downstream from the fuel processor,as is schematically illustrated in dash-dot lines in FIG. 1. It is alsowithin the scope of the disclosure that purification region 24 mayinclude portions within and external fuel processor 12.

In the context of a fuel processor, or fuel processing assembly, that isadapted to produce a product hydrogen stream that will be used as afeed, or fuel, stream for a fuel cell stack, the fuel processorpreferably is adapted to produce substantially pure hydrogen gas, andeven more preferably, the fuel processor is adapted to produce purehydrogen gas. For the purposes of the present disclosure, substantiallypure hydrogen gas is greater than 90% pure, preferably greater than 95%pure, more preferably greater than 99% pure, and even more preferablygreater than 99.5% pure. Suitable fuel processors for producing streamsof at least substantially pure hydrogen gas are disclosed in U.S. Pat.Nos. 6,319,306, 6,221,117, 5,997,594, 5,861,137, pending U.S. patentapplication Ser. No. 09/802,361, which was filed on Mar. 8, 2001 and isentitled “Fuel Processor and Systems and Devices Containing the Same,”and U.S. patent application Ser. No. 10/407,500, which was filed on Apr.4, 2003, is entitled “Steam Reforming Fuel Processor,” and which claimspriority to U.S. Provisional Patent Application Ser. No. 60/372,258. Thecomplete disclosures of the above-identified patents and patentapplications are hereby incorporated by reference for all purposes.

Product hydrogen stream 14 may be used in a variety of applications,including applications where high purity hydrogen gas is utilized. Anexample of such an application is as a fuel, or feed, stream for a fuelcell stack. A fuel cell stack is a device that produces an electricalpotential from a source of protons, such as hydrogen gas, and anoxidant, such as oxygen gas. Accordingly, a fuel cell stack may beadapted to receive at least a portion of product hydrogen stream 14 anda stream of oxygen (which is typically delivered as an air stream), andto produce an electric current therefrom. This is schematicallyillustrated in FIG. 2, in which a fuel cell stack is indicated at 40 andproduces an electric current, which is schematically illustrated at 41.In such a configuration, in which the fuel processor or fuel processingassembly is coupled to a fuel cell stack, the resulting system may bereferred to as a fuel cell system 42 because it includes a fuel cellstack and a source of fuel for the fuel cell stack. It is within thescope of the present disclosure that fuel processors and heatingassemblies according to the present disclosure may be used inapplications that do not include a fuel cell stack.

When stream 14 is intended for use in a fuel cell stack, compositionsthat may damage the fuel cell stack, such as carbon monoxide and carbondioxide, may be removed from the hydrogen-rich stream, if necessary,such as by purification region 24. For fuel cell stacks, such as protonexchange membrane (PEM) and alkaline fuel cell stacks, the concentrationof carbon monoxide is preferably less than 10 ppm (parts per million).Preferably, the concentration of carbon monoxide is less than 5 ppm, andeven more preferably, less than 1 ppm. The concentration of carbondioxide may be greater than that of carbon monoxide. For example,concentrations of less than 25% carbon dioxide may be acceptable in someembodiments. Preferably, the concentration is less than 10%, and evenmore preferably, less than 1%. While not required, especially preferredconcentrations are less than 50 ppm. The acceptable minimumconcentrations presented herein are illustrative examples, andconcentrations other than those presented herein may be used and arewithin the scope of the present disclosure. For example, particularusers or manufacturers may require minimum or maximum concentrationlevels or ranges that are different than those identified herein.

Fuel cell stack 40 contains at least one, and typically multiple, fuelcells 44 that are adapted to produce an electric current from anoxidant, such as air, oxygen-enriched air, or oxygen gas, and theportion of the product hydrogen stream 14 delivered thereto. A fuel cellstack typically includes multiple fuel cells joined together betweencommon end plates 48, which contain fluid delivery/removal conduits,although this construction is not required to all embodiments. Examplesof suitable fuel cells include proton exchange membrane (PEM) fuel cellsand alkaline fuel cells. Others include solid oxide fuel cells,phosphoric acid fuel cells, and molten carbonate fuel cells.

The electric current produced by stack 40 may be used to satisfy theenergy demands, or applied load, of at least one associatedenergy-consuming device 46. Illustrative examples of devices 46 include,but should not be limited to, motor vehicles, recreational vehicles,construction or industrial vehicles, boats or other seacraft, tools,lights or lighting assemblies, appliances (such as household or otherappliances), households or other dwellings, offices or other commercialestablishments, computers, signaling or communication equipment, etc.Similarly, fuel cell stack 40 may be used to satisfy the powerrequirements of fuel cell system 42, which may be referred to as thebalance-of-plant power requirements of the fuel cell system. It shouldbe understood that device 46 is schematically illustrated in FIG. 2 andis meant to represent one or more devices, or collection of devices,that are adapted to draw electric current from the fuel cell system.

Fuel cell stack 40 may receive all of product hydrogen stream 14. Someor all of stream 14 may additionally, or alternatively, be delivered,via a suitable conduit, for use in another hydrogen-consuming process,burned for fuel or heat, or stored for later use. As an illustrativeexample, a hydrogen storage device 50 is shown in dashed lines in FIG.2. Device 50 is adapted to store at least a portion of product hydrogenstream 14. For example, when the demand for hydrogen gas by stack 40 isless than the hydrogen output of fuel processor 12, the excess hydrogengas may be stored in device 50. Illustrative examples of suitablehydrogen storage devices include hydride beds and pressurized tanks.Although not required, a benefit of fuel processing assembly 10 or fuelcell system 42 including a supply of stored hydrogen is that this supplymay be used to satisfy the hydrogen requirements of stack 40, or theother application for which stream 14 is used, in situations when fuelprocessor 12 is not able to meet these hydrogen demands. Examples ofthese situations include when the fuel processor is starting up from acold, or inactive state, ramping up (being heated and/or pressurized)from an idle state, offline for maintenance or repair, and when the fuelcell stack or application is demanding a greater flow rate of hydrogengas than the maximum available production from the fuel processor.Additionally or alternatively, the stored hydrogen may also be used as acombustible fuel stream to heat the fuel processing assembly or fuelcell system. Fuel processing assemblies that are not directly associatedwith a fuel cell stack may still include at least one hydrogen-storagedevice, thereby enabling the product hydrogen streams from these fuelprocessing assemblies to also be stored for later use.

Fuel cell system 42 may also include a battery 52 or other suitableelectricity-storing device that is adapted to store the electricpotential, or power output, produced by stack 40. Similar to the abovediscussion regarding excess hydrogen, fuel cell stack 40 may produce apower output in excess of that necessary to satisfy the load exerted, orapplied, by device 46, including the load required to power fuel cellsystem 42. In further similarity to the above discussion of excesshydrogen gas, this excess power output may be used in other applicationsoutside of the fuel cell system and/or stored for later use by the fuelcell system. For example, the battery or other storage device mayprovide power for use by system 42 during startup or other applicationsin which the system is not producing electricity and/or hydrogen gas. InFIG. 2, flow-regulating structures are generally indicated at 54 andschematically represent any suitable manifolds, valves, controllers,switches and the like for selectively delivering hydrogen and the fuelcell stack's power output to device 50 and battery 52, respectively, andto draw the stored hydrogen and stored power output therefrom.

In FIG. 1, fuel processor 12 is shown including a shell 68 in which atleast the hydrogen-producing region, and optionally the purificationregion, is contained. Shell 68, which also may be referred to as ahousing, enables the components of the steam reformer or other fuelprocessing mechanism to be moved as a unit. It also protects thecomponents of fuel processor 12 from damage by providing a protectiveenclosure and reduces the heating demand of the fuel processing assemblybecause the components of the fuel processor may be heated as a unit.Shell 68 may, but does not necessarily, include insulating material 70,such as a solid insulating material, blanket insulating material, and/oran air-filled cavity. It is within the scope of the disclosure, however,that the fuel processor may be formed without a housing or shell. Whenfuel processor 12 includes insulating material 70, the insulatingmaterial may be internal the shell, external the shell, or both. Whenthe insulating material is external a shell containing theabove-described reforming and/or purification regions, fuel processor 12further may include an outer cover or jacket 72 external the insulation,as schematically illustrated in FIG. 1.

It is further within the scope of the disclosure that one or more of thecomponents of fuel processing assembly 10 may either extend beyond theshell or be located external at least shell 68. For example, and asdiscussed, purification region 24 may be located external shell 68, suchas with the purification region being coupled directly to the shell (asschematically illustrated in FIG. 3) or being spaced-away from the shellbut in fluid communication therewith by suitable fluid-transfer conduits(as indicated in dash-dot lines in FIG. 1). As another example, aportion of hydrogen-producing region 19 (such as portions of one or morereforming catalyst beds) may extend beyond the shell, such as indicatedschematically with a dashed line representing an alternative shellconfiguration in FIG. 1.

Illustrative examples of fuel cell systems and fuel processingassemblies have been schematically illustrated in FIGS. 1-3. Thesesystems may include additional components, such as air/oxidant suppliesand delivery systems, heat exchange assemblies and/or sources,controllers, sensors, valves and other flow controllers, powermanagement modules, etc. It is within the scope of the presentdisclosure to selectively include one or more of these components.Similarly, although a single fuel processor 12 and/or a single fuel cellstack 40 are shown in FIGS. 1-3, it is within the scope of thedisclosure that more than one of either or both of these components maybe used.

As also shown in FIGS. 1-3, fuel processing assemblies (and fuel cellsystems) according to the present disclosure include a heating assembly60 that is adapted to heat at least the hydrogen-producing region, orreforming region, 19 of the fuel processor. In systems according to thepresent disclosure, heating assembly 60 includes a burner assembly 62and may be referred to as a combustion-based, or combustion-driven,heating assembly. Heating assembly 60 is adapted to receive at least onefuel stream 64 and to combust the fuel stream in the presence of air toprovide a hot combustion stream 66 that may be used to heat at least thehydrogen-producing region 19 of the fuel processor. Stream 66 may alsobe referred to as a heated exhaust stream. As discussed in more detailherein, air may be delivered to the heating assembly via a variety ofmechanisms. In FIG. 3, an air stream 74 is shown in solid lines;however, it is within the scope of the disclosure for the air stream toadditionally or alternatively be delivered to the heating assembly withat least one of the fuel streams 64 for the heating assembly 60. It iswithin the scope of the disclosure that combustion stream 66 mayadditionally or alternatively be used to heat other portions of the fuelprocessing assembly and/or fuel cell systems with which heating assembly60 is used.

In FIGS. 1-3, heating assembly 60 is shown in an overlappingrelationship with fuel processor 12 to graphically represent that it iswithin the scope of the disclosure that the heating assembly may belocated partially or completely within fuel processor 12, such as beingat least partially within shell 68, and/or that at least a portion, orall, of the heating assembly may be located external the fuel processor.In this latter embodiment, the hot combustion gases from the burnerassembly will be delivered via suitable heat transfer conduits to thefuel processor or other portion of the system(s) to be heated.

As indicated in dashed lines in FIG. 3, fuel processors 12 according tothe present disclosure may include a vaporization region 69 that isadapted to receive a liquid feed stream 16 (or a liquid component offeed stream 16, such as a stream of water 17 or a stream of a liquidcarbon-containing feedstock 18) and to vaporize the feed stream (orportion thereof) prior to delivery to hydrogen-producing region 19 offuel processor 12. As indicated schematically in FIG. 3, heatedcombustion stream 66 from the heating assembly may be used to vaporizethe feed stream in vaporization region 69 and/or otherwise heat the feedstream. It is within the scope of the disclosure that fuel processor 12may be constructed without a vaporization region and/or that the fuelprocessor is adapted to receive a feed stream that is gaseous or thathas already been vaporized.

As discussed, many conventional fuel processors, such as steam andautothermal reformers and pyrolysis and partial oxidation reactors,require a carbon-containing feedstock that is used in thehydrogen-producing reaction, and then a separate fuel stream, typicallya carbon-containing feedstock, that is used as a fuel source for theheating assembly. As such, these conventional fuel processing assembliesrequire a separate source, pump, or other delivery assembly, transportconduits, and flow-regulating devices, etc. According to an aspect ofthe present disclosure, a liquid-phase carbon-containing feedstock 84may be used for both carbon-containing feedstock portion 18 of feedstream 16 for reforming region 19 and carbon-containing feedstockportion 65 of fuel stream 64 for heating assembly 60, such asschematically illustrated in FIG. 4. This dual use of carbon-containingfeedstock 84 is not required to all embodiments of the presentdisclosure. In the illustrative example shown in FIG. 4, liquidcarbon-containing feedstock 84 is delivered to both heating assembly 60and hydrogen-producing region 19. FIG. 4 has been shown in a fragmentaryview because fuel processor 12 may have a wide variety ofconfigurations, such as configurations that do not include apurification region, that utilize more than one type or number ofpurification mechanism, etc. It is intended that the fragmentary fuelprocessor shown in FIG. 4 (and subsequent figures) schematicallyrepresents any of these configurations, as well as any of the steamreformers and other fuel processors described, illustrated and/orincorporated herein.

FIG. 5 is similar to FIG. 4, except that the liquid carbon-containingfeedstock 84 is delivered as a single stream to valve assembly 86, inwhich the carbon-containing feedstock is selectively delivered to atleast one of the heating assembly and the hydrogen-producing region.Valve assembly 86 may include any suitable structure for selectivelydividing the stream of carbon-containing feedstock between the heatingassembly and the hydrogen-producing region, The range of possibleconfigurations includes the heating assembly receiving all of thecarbon-containing feedstock, the hydrogen-producing region receiving allof the carbon-containing feedstock, or both the heating assembly and thehydrogen-producing region receiving carbon-containing feedstock. Asdiscussed herein, the distribution of the carbon-containing feedstockdepends at least in part upon the particular carbon-containing feedstockbeing used, whether byproduct stream 28 is also used as a fuel for atleast a portion of heating assembly 60 (such as a primary burnerassembly 58), and the particular mode of operation of the fuelprocessor, such as an idle mode, a startup mode, or a hydrogen-producingmode.

The distribution of liquid carbon-containing feedstock 84 between thehydrogen-producing region and the heating assembly may be manuallycontrolled. However, in many embodiments, it may be desirable for thedistribution to be predetermined and/or at least partially automated,such as by including a controller 88 that selectively regulates thedelivery of feedstock 84 between the hydrogen-producing region and theheating assembly. An example of a suitable controller for a steamreforming fuel processor is disclosed in U.S. Pat. No. 6,383,670, thecomplete disclosure of which is hereby incorporated by reference. Insome embodiments, controller 88 and/or valve assembly 86 may beconfigured to allow a predetermined initial volume of carbon-containingfeedstock into heating assembly 60, as will be discussed in greaterdetail herein.

As discussed previously, in the context of a steam reformer or otherfuel processor that produces hydrogen gas from water and acarbon-containing feedstock, feed stream 16 may be at leastsubstantially, and typically entirely, comprised of a mixture of waterand a liquid-phase carbon-containing feedstock 84 that is preferablymiscible in, or with, water. As such, a single (composite) feed stream90 containing water 17 and carbon-containing feedstock 84 can beconsumed as both the hydrogen-producing feed stream 16 for the reformingreaction, as well as the heating assembly fuel stream 64. Furtherreduction in the supplies, delivery systems, flow regulators, deliveryconduits and the like may be achieved according to another aspect of thepresent disclosure by feed stream 16 and fuel stream 64 both containingthe same liquid carbon-containing feedstock 84 and water 17, with thecarbon-containing feedstock preferably being miscible in water. This isschematically illustrated in FIGS. 6 and 7, in which this compositestream is indicated at 90. Streams 16 and 64 may have nearly, orcompletely, identical compositions, and may be entirely formed fromstream 90. It is within the scope of the disclosure, however, that atleast one of streams 16 and 64 may have at least one additionalcomponent or additional amount of water or carbon-containing feedstockadded thereto prior to consumption of the stream by the heating assemblyor hydrogen-producing region. Similarly, it is within the scope of thepresent disclosure that additional streams may deliver additionalcomponents or additional amounts of water or carbon-containing feedstockto the heating assembly or the fuel processor.

Similar to the previously discussed alternatives of FIGS. 4 and 5 (whereonly the carbon-containing feedstock component 84 of feed stream 16 wasdelivered to heating assembly 60 rather than both the carbon-containingfeedstock 84 and the water 17), composite feed stream 90 may beselectively delivered to heating assembly 60 and hydrogen-producingregion 19 in separate streams from the same source or from differentsources, as schematically illustrated in FIG. 6. Alternatively, and asschematically illustrated in FIG. 7, a single composite feed stream 90may be delivered to the fuel processing assembly, and more specificallyto a valve assembly 86, where the stream is selectively divided betweenthe heating assembly and the hydrogen-producing region. A controller 88,which may be a manual controller or a computerized or other electroniccontroller or preprogrammed controller, is also shown in dashed lines inFIG. 7. Controller 88 may be located internal or external fuel processor12, and/or may include both internal and external components.

The relative amounts of water 17 and liquid carbon-containing feedstock84 in composite feed stream 90 may vary within the scope of the presentdisclosure. For example, the ratio may depend upon such factors as theparticular carbon-containing feedstock being used, thehydrogen-producing mechanism being used in the fuel processor, userpreferences, the catalyst being utilized, the demand for hydrogen gas,the efficiency of the reforming catalyst, etc. The relativeconcentrations of these components may be expressed in terms of a ratioof water to carbon. When feedstock 84 is methanol, a 1:1 molar ratio ofsteam to carbon has proven effective. When feedstock 84 is ethanol, aratio of 2-3:1 has proven effective. When feedstock 84 is a hydrocarbon,a ratio of approximately 3:1 is typically used. However, theillustrative ratios described above are not meant to be exclusive ratioswithin the scope of the disclosure, and others, including greater andlesser ratios, may be used.

In FIG. 8, a variation of the configuration of FIG. 7 is shown toillustrate that it is within the scope of the present disclosure thatvalve assembly 86 may be located either internal or external fuelprocessor 12, FIG. 8 also illustrates that when the fuel processorincludes or is otherwise associated with a purification region 24 thatproduces a gaseous byproduct stream 28, the gaseous byproduct stream 28may be delivered to the heating assembly to be used as a gaseous fuelfor the heating assembly. This gaseous fuel may supplement the liquidfuel discussed above (such as carbon-containing feedstock 84 orcomposite feed stream 90), or may itself contain sufficient heatingvalue for certain steam reformers or other fuel processors and/orcertain operating configurations of the fuel processors.

Fuel processor 12, heating assembly 60, and feedstock delivery system 22may be configured in any of the arrangements described above. In someembodiments, features or aspects from one or more of the above describedconfigurations may be combined with each other and/or with additionalfeatures described herein. For example, it is within the scope of thepresent disclosure that fuel processors 12 which include at least onepurification region 24 may (but are not required to) house thehydrogen-producing region 19 and at least a portion of the purificationregion together in a common housing, with this housing optionally beinglocated within the shell 68 of the fuel processor. This is schematicallyillustrated in FIG. 9, in which reference numeral 25 generally indicatesa hydrogen-producing region 19 of a fuel processor, with thehydrogen-producing region being contained within a housing, or vessel,27 that contains at least the reforming (or other) catalyst 23 used toproduce the mixed gas stream from the feed stream that is delivered tothe hydrogen-producing region.

As indicated in dashed lines in FIG. 9, shell 27 (and thereby region 25)may, but is not required to, also include a purification region 24. Forexample, as illustrated in dashed lines in FIG. 9, the purificationregion, when present in the housing, may include one or morehydrogen-selective membranes 30 and/or a chemical carbon monoxideremoval assembly 32. Accordingly, region 25 may be described as ahydrogen-producing and purifying region when it contains both ahydrogen-producing region 19 and a purification region 24. It is withinthe scope of the disclosure that any of the regions 19 and 24 described,illustrated and/or incorporated herein may be used in region 25. Whenregion 25 does not include a purification region, it may simply bedescribed as a hydrogen-producing region 19 that includes a housing 27.When housing 27 includes a purification region 24, it is still withinthe scope of the present disclosure that the fuel processing assemblymay include one or more additional purification regions (such as whichmay include the same or different purification devices/mechanisms)external (i.e., downstream from) housing 27. The fuel processingassemblies illustrated herein thereby include a hydrogen-producingregion that is contained in a housing, with this housing optionally alsocontaining a purification region.

Some combustible fuel streams 64 that may be delivered to heatingassembly 60 are liquid-phase fuel streams at the operating parameters atwhich the fuel stream is delivered to heating assembly 60. As anon-exclusive example, the fuel stream may be delivered to the heatingassembly as a liquid fuel stream at a temperature in the range ofapproximately 25° C. to approximately 100° C., although temperaturesabove and below this illustrative range may be used without departingfrom the scope of the present disclosure. As used herein, “liquid” or“liquid-phase” is meant to refer to fuel streams that include at least amajority, if not most or even all, or nearly all, of the fuel in theliquid phase at the operating parameters at which the fuel stream isdelivered to the heating assembly. Additionally, when fuel stream 64includes carbon-containing feedstock 84 or composite stream 90 havingcarbon-containing feedstock and water, fuel stream 64 delivered toheating assembly 60 may be in the liquid phase at operating parametersat which it is delivered to the heating assembly. The operatingparameters discussed above are not intended to be exclusive examples.Instead, they are meant to illustrate typical parameters, withparameters outside of these ranges still being within the scope of thedisclosure. In many applications, such as heating assembliesincorporated in fuel processing assemblies for use in portable or mobileuses, the operating parameters for delivery of fuel stream 64 may varywidely depending on the environmental conditions in which the fuelprocessing assembly is used. For example, fuel processing assemblies maydeliver fuel stream 64 to heating assembly 60 at temperatures rangingfrom lower than 0° C. to higher than 100° C.

Illustrative, non-exclusive examples of other temperature ranges withinwhich the fuel processing assemblies may be used include temperatures ofless than 30° C., less than 20° C., less than 10° C., less than −10° C.,less than −20° C., less than −30° C., less than −40° C., temperatures inthe range of −50° C. and 100° C., temperatures in the range of −50° C.and 50° C., temperatures in the range of −50° C. and 30° C.,temperatures in the range of −30° C. and 50° C., and temperatures in therange of −30° C. and 30° C. As discussed, during startup of the fuelprocessing assembly, the heating assembly is adapted to receive andinitiate combustion of a liquid fuel stream. Some liquid fuels may notbe liquids in regions of the illustrative temperature ranges describedabove, and accordingly, the composition of the liquid fuel to be usedmay be selected with factors that include the expected ambienttemperature around the fuel processing assembly. For example, methanolwill not be a liquid at 100° C.

In FIG. 10, an illustrative heating assembly 60 within the scope of thepresent disclosure is illustrated schematically. Heating assembly 60includes burner assembly 62 and may include associated inlets, outlets,and other features appropriate and consistent with the heating assemblydescription provided herein. As indicated schematically in FIG. 10,burner assemblies 62 according to the present disclosure include astart-up burner assembly 56 and, in some embodiments, also may include aprimary, or main, burner assembly 58. As the name implies, the start-upburner assembly is adapted to heat at least the hydrogen-producingregion of the fuel processor to a suitable hydrogen-producingtemperature. The primary, or main, burner is adapted to providecontinued heating to at least the hydrogen-producing region of the fuelprocessor during continued hydrogen-producing operation of the fuelprocessor. The primary burner may be adapted to consume a gaseous fuelstream, with this gaseous fuel stream being partially or completelyformed from a portion of the mixed gas stream produced by thehydrogen-producing region. It is within the scope of the presentdisclosure that the start-up and primary burner assemblies, when bothpresent in a particular embodiment, may be separate assemblies and/ormay share one or more components.

Heating assembly 60 is illustrated in FIG. 10 in isolation from fuelprocessor 12 and the remaining components of fuel processing assembly10. However, as discussed above, heating assembly 60, such as theheating assembly shown schematically in FIG. 10, may be in thermalcommunication with the reforming region or may otherwise be adapted toheat portions of the fuel processing assembly including the reformingregion. As discussed above, heating assembly 60 may be disposed withinshell 68 of fuel processor 12 or may be located at least partially, orcompletely, external of the shell. Appropriate conduits, conductingmaterials, and other apparatus may be provided to communicate thethermal energy in combustion stream 66 to the reforming region of thefuel processor.

As illustrated schematically in FIG. 10, heating assembly 60 includes atleast one fuel chamber 76 and at least one heating and ignition source78 and is adapted to receive at least one air stream 74. Air stream 74may be positively delivered to the heating assembly, such as with ablower, fan, compressor, pressurized source, or other suitable device orassembly for delivering an air stream to the heating assembly.Additionally, or alternatively, the heating assembly may be sufficientlyopen to the environment to draw or otherwise be exposed to a suitableflow of air to support combustion in the heating assembly.

The at least one fuel chamber is configured to receive at least aportion of fuel stream 64. Fuel stream 64 includes a carbon-containingfeedstock 65 and may include additional components such as water, air,oxygen, hydrogen, or other components that are combustible,non-combustible, and/or necessary for combustion, such as air or oxygen.

While a single fuel stream 64 is shown in FIG. 10, it is within thescope of the present disclosure that more than one stream 64 may be usedand that the additional streams may supply the same or differentcarbon-containing feedstocks, other combustible fuels, air, or othercomponents. This is schematically illustrated by the inclusion of asecond fuel stream 64 in dashed lines in FIG. 10. Additionally, asdiscussed above, fuel stream 64 may include liquid, carbon-containingfeedstock 84 that is the same carbon-containing feedstock delivered tofuel processor 12. Similarly, fuel stream 64 may include compositestream 90 that includes carbon-containing feedstock 84 and water 17, andwhich may have the same, or essentially the same composition as the feedstream for the hydrogen-producing region of the fuel processor.

As discussed, heating assembly 60 also includes a heating and ignitionsource 78. Source 78 is adapted to heat and initiate combustion of thecarbon-containing feedstock 65 (or 84) in fuel stream 64. Heating andignition source 78 may be disposed or otherwise positioned external tofuel chamber 76, as shown in solid lines, may be disposed within fuelchamber 76, as shown in dashed lines, or may be disposed partiallyinside and partially outside of fuel chamber 76. Heating and ignitionsource 78 may include any suitable structure or device for heating andigniting the fuel stream in the presence of air to initiate combustionthereof, In some embodiments, heating and ignition source 78 may includemore than one device.

Examples of suitable heating and ignition sources 78 include at leastone of a spark plug, a glow plug, a pilot light, a combustion catalyst,glow plugs in combination with combustion catalysts, electrically heatedceramic igniters, and the like, In some embodiments, heating andignition source 78 includes an electrical resistance heating elementeither alone or in combination with an igniter, such as a spark plug. Aglow plug is one example of an electrical resistance heating elementthat may be used alone to both heat and ignite the carbon-containingfuel received by the fuel chamber. Heating and ignition source 78 mayinclude an electrical resistance heating element configured to be heatedto a temperature sufficiently hot, also referred to as a red hot orglowing hot temperature, to ignite the carbon-containing fuel in fuelchamber 76.

FIG. 10 also illustrates schematically that heating assembly 60 mayinclude an ignition region 80 and a combustion region 82, schematicallyrepresented by the dashed line dividing the two regions. In suchembodiments, the carbon-containing fuel disposed in the fuel chamber maybe mixed with air and ignited in the ignition region 80 and combusted toproduce heated combustion stream 66, which may be exhausted from heatingassembly 60 to heat at least the reforming region of fuel processor 12.It is within the scope of the present disclosure that the combustioninitiated in ignition region 80 may extend to other locations withinheating assembly 60 and/or fuel processing assembly 10. For example, thecombustion may continue in the ignition region, and may also extend tocombustion region 82 such that after ignition combustion occurs in boththe combustion region and the ignition region. Additionally, due to thedispersion of the fuel vapor, combustion may occur in other portions ofthe fuel processing assembly. As used herein, ignition region 80 is usedto refer to an area or region in fuel chamber 76 that is smaller thanthe entirety of the fuel chamber, That is, ignition region 80 is asubset of fuel chamber 76 that may be physically defined or may be anarea of fuel chamber 76, such as a particular end region, corner region,etc.

As illustrated in solid lines in FIG. 10, fuel stream 64 is delivered asa volume of liquid, at least a substantial portion of which (if not allof which) remains as a liquid fuel supply within the fuel chamber untilit is consumed to support combustion within the fuel chamber, asdiscussed in more detail herein. Fuel stream 64 may be delivered to anaperture or fill port of the fuel chamber through a suitable fluidconduit, with the liquid fuel thereafter flowing within the fuelchamber, such as under the force of gravity adsorptive/wicking forcesapplied by any structures within the fuel chamber, etc. It is within thescope of the present disclosure that the heating assembly may include atleast one distribution conduit that extends within the fuel chamber andthrough which the liquid fuel stream flows prior to being dispensed fromthe distribution conduit within the fuel chamber. The distributionconduit may include apertures or other outlets along its length, mayinclude an outlet (such as at its distal end within the fuel chamber),and/or may include one or more branches to further distribute the liquidfuel stream within the fuel chamber. While not required to allembodiments, the distribution conduit, when used, may be adapted toselectively deliver at least a portion of the liquid fuel streambeneath, or proximate to, the heating and ignition source, to distributethe liquid fuel stream to one or more selected regions of the fuelchamber, etc. When the fuel chamber includes a transport medium, asdescribed herein, a distribution conduit may (but is not required to be)used to deliver the liquid fuel stream through at least a portion of thetransport medium prior to dispensing the liquid fuel from the conduitand into the fuel chamber. In FIG. 10, a distribution conduit isschematically illustrated at 67 and is shown extending within the fuelchamber at least to a region proximate, or even beneath, the heating andignition source.

In operation, and as described above, fuel stream 64 may be delivered toheating assembly 60 as a liquid, or at least partially in a liquidphase. Fuel stream 64 may be delivered to fuel chamber 76 underoperating conditions, or delivery conditions, that include a firsttemperature and a first pressure. The carbon-containing feedstock(s)delivered to the fuel chamber may have a flash point, or minimumignition temperature, that is higher than the first temperature at whichthe carbon-containing feedstock(s) is delivered to the fuel chamber. Asused herein, “flash point” refers to the minimum temperature at whichthe vapor pressure of the liquid is sufficient to form an ignitablemixture with air near the surface of the liquid.

The flash point for the fuel stream received by fuel chamber 76 maydepend upon such factors as the carbon-containing feedstock in the fuelstream, the relative concentrations of carbon-containing feedstock andother components in the fuel stream, the conditions in the fuel chamber,etc. Using composite stream 90 as an exemplary fuel stream 64, FIG. 11illustrates the flash point of a methanol-water solution for variousconcentrations of methanol in water. FIG. 11 is representative of flashpoint curves that may be generated for the various fuel streamcompositions that may be used with the heating assembly of the presentdisclosure, with a stream of methanol and water being an illustrative,but not exclusive, example of a suitable fuel stream. As illustrated inFIG. 11, the flash point temperature decreases with increasingconcentrations of methanol. As discussed, other carbon-containingfeedstocks may be used, such as other carbon-containing feedstocks thatare miscible with water. These other carbon-containing feedstocks mayhave similar flash point curves for solutions of the feedstock andwater, but it is not required that all carbon-containing feedstockswithin which the heating assemblies and fuel processing assemblies ofthe present disclosure have a flash point curve that corresponds or issimilar to that of methanol-water mixtures.

While the flash point refers to the minimum temperature at which aliquid fuel will have a vapor pressure above its surface sufficient toform an ignitable mixture with air, whether the mixture will ignite isdependent upon the concentration of the combustible fuel vapor in theair at the location of the ignition source. For example, if the ignitionsource is spaced-apart from the surface of the liquid carbon-containingfeedstock, a number of factors may have diluted the concentration of thecombustible fuel vapor. The lower flammability limit is often used torefer to the minimum concentration of the combustible fuel vapor in airfor which a flame can propagate. As used herein, “ignition vaporpressure” may be used to refer to the minimum vapor pressure at whichignition of the fuel in air will occur.

The temperature of the liquid carbon-containing feedstock in fuelchamber 76 necessary to produce an ignitable vapor concentration (i.e.,a concentration at least equal to the lower flammability limit) may behigher than the flash point temperature and will be referred to hereinas the ignition temperature. While the ignition temperature accounts forenvironmental factors such as availability of fresh air in the vaporspace above the liquid fuel in the area adjacent the ignition source andthe ability of the fuel vapor to exit the fuel chamber, the ignitiontemperature will be referred to herein as a property of thecarbon-containing fuel.

The fuel stream may enter the fuel chamber at a first temperature andmay have an ignition temperature greater than the first temperature. Insome embodiments, the carbon-containing fuel delivered to the fuelchamber may have an ignition partial pressure, and the carbon-containingfuel in the fuel chamber may have an initial partial pressure less thanits ignition partial pressure. In some applications of heating assembly60, the first temperature (delivery temperature) of fuel stream 64 maybe such that there is substantially no carbon-containing feedstock inthe vapor phase. In other applications, the fuel stream may be deliveredat a first temperature at which there is some carbon-containingfeedstock in the vapor phase. However, in many applications theconcentration of carbon-containing feedstock in the vapor phase at thefirst temperature will not be sufficient to form a flammable mixture atthe location of heating and ignition source 78. That is, the firsttemperature will be less than the ignition temperature of thecarbon-containing fuel. Cold weather applications and configurationswhere fuel stream 64 includes composite stream 90 having water 17 andcarbon-containing feedstock 84 are exemplary, though not exclusive,applications where the first temperature will not yield sufficientlyhigh concentrations of carbon-containing feedstock vapor, or fuel vapor,to form an ignitable mixture at the heating and ignition source.

Referring now to FIG. 12, a somewhat schematic side view of a fuelprocessing assembly 10 is illustrated, including a partial cutaway viewof heating assembly 60. As shown, fuel stream 64 delivers acarbon-containing liquid fuel to heating assembly 60. Thecarbon-containing fuel may include the same carbon-containing feedstock84 that is delivered to the reforming region 19 or may include anothercarbon-containing feedstock 65. Fuel stream 64 may also delivercomposite stream 90 having carbon-containing feedstock 84 and water 17,which may, but is not required to, have the same composition and waterto carbon ratio as the feed stream for the reforming region.

Start-up burner assembly 56 of heating assembly 60 includes a fuelchamber 76 that is adapted to receive the fuel stream. Fuel chamber 76includes a bottom 92 and side walls 94. As illustrated, fuel chamber 76has a partially, or completely, open top 95, and thereby forms an openreservoir for retaining the liquid fuel delivered thereto. Air stream 74may be delivered (by blowers, fans, or other suitable devices) and/ormay naturally flow to fuel chamber 76 from the environment through opentop 95. As illustrated in FIG. 12, the reforming region 19 or otherportion of the fuel processing assembly to be heated by combustionexhaust stream 66 will typically be located above, and often relativelyclose to, the open top of the fuel chamber. This enables the combustionstream to heat this structure as the stream naturally flows from thefuel chamber. As discussed, blowers, fans and other suitable structuresmay additionally or alternatively be used to promote the delivery of theheated combustion stream to reforming region 19 and/or other regions ofthe fuel processing assembly.

In some embodiments, fuel chamber 76 may include a full or partial topmember 104 for enclosing, either completely or partially, the fuelchamber. When fuel chamber 76 includes a full, or closed, top member toform a substantially closed combustion chamber, fuel chamber 76 also mayinclude one or more air inlets 99 to allow air to enter the fuel chamberfor combustion, such as air stream 74 described above, and also mayinclude one or more exhaust ports 101. An example of such an embodimentis schematically illustrated in FIG. 13 and may include any of theinternal configurations and components discussed and/or illustratedherein. The air inlets and exhaust ports may be configured for naturalair flow or may be coupled to pumps, blowers, compressors, valves, orother equipment for controlled or pressurized fluid flow. An inlet port99 for air stream 74 is also shown in dashed lines in FIG. 12 tographically depict that (at least partially) open top fuel chambers alsomay include one or more inlet and/or exhaust ports. The closed top ofthe illustrated heating assembly of FIG. 13 may produce more radiantheat than a comparable open top heating assembly, and through the use ofexhaust port(s) 101 (and associated fluid conduits extending therefrom),may be configured to deliver combustion exhaust stream 66 to one or moreselected regions or structures of the fuel processing assembly,including regions that would be more difficult to suitably heat merelyby the convective flow of the heated exhaust stream through an open topof the fuel chamber.

With continued reference to FIG. 12, fuel chamber 76 may be described asincluding a liquid fuel region 96 and a fuel vapor region 98. Asillustrated, fuel chamber 76 is an open reservoir and fuel vapor region98 is defined by the surface of the liquid fuel in the liquid fuelregion 96 and by side walls 94 of fuel chamber 76, but is unbounded ontop (i.e., theoretically the fuel vapor region extends as far as thefuel vapor can dissipate within the fuel processing assembly). Inembodiments where fuel chamber 76 includes a top member, whether full orpartial, fuel vapor region 98 may be said to be at least partiallybounded on the top by the full or partial top member.

Heating assembly 60 also includes a heating and ignition source 78, asdescribed briefly above. As illustrated in FIG. 12, heating and ignitionsource 78 takes the form of an electrical resistance heating element 100that is disposed completely in fuel vapor region 98. As shown, theheating and ignition source is illustrated being positioned above theliquid fuel region of the fuel chamber. However, it is within the scopeof the present disclosure that at least a portion of the heating andignition source be disposed in liquid fuel region 96, as illustrated indashed lines in FIG. 12. Similarly, it is within the scope of thepresent disclosure that other functionally suitable structures may beused for heating and ignition source 78, with the electrical resistanceheating element, and its illustrated coiled configuration, merely beingillustrative, non-exclusive examples. While heating and ignition source78 is shown adjacent to one end of heating assembly 60, it is within thescope of the present disclosure that heating and ignition source 78 maybe disposed anywhere within heating assembly 60 where at least a portionof it may be in sufficient contact with fuel vapor to ignite thecarbon-containing fuel in the fuel chamber. As illustrative,non-exclusive examples, the heating and ignition source may bepositioned along a lateral wall of the fuel chamber, may be locatedwithin a perimeter region of the fuel chamber, may be located within acentral region of the fuel chamber, etc.

With continuing reference to FIG. 12, heating and ignition source 78 isillustrated as being in a coiled configuration and as a unitary device.Other configurations are within the scope of the present disclosure. Forexample, a unitary heating and ignition source 78 may be linear, mayinclude linear and curved portions, or may be otherwise curled, bent, orconfigured in other shapes or configurations. Additionally oralternatively, heating and ignition source 78 may include more than onedevice, such as two, three, or more components. For example, a firstdevice may be configured to heat the liquid carbon-containing fuel inthe fuel chamber while a second device may be configured to provide theignition source. The ignition source may be a spark plug or otherintermittent, or selectively actuated, ignition source or may be a glowplug or other source that provides a red hot surface of sufficienttemperature to ignite the fuel vapor in the fuel chamber. As anotherexample, two or more complete heating and ignition devices may be used,such as two or more spaced-apart resistance heating elements.

As discussed, heating and ignition source 78 may include one or moredevices. Regardless of the configuration, heating and ignition source 78can be understood to provide a heating area and an ignition area. Theheating area and the ignition area may be separate portions of thesource 78, they may be the same portions of the source, or they mayinclude overlapping portions of the source. In a unitary heating andignition source disposed entirely in the fuel vapor region, for example,the heating area and the ignition area may be coextensive. Inmulti-component heating and ignition sources, one component may be (atleast primarily) configured to heat the liquid while the other componentis (at least primarily) configured to ignite the vapor. Additionally oralternatively, a unitary device may be configured with two or moreportions of different constructions, such as of different materials, toimpart different characteristics or features as discussed herein. Onesuch portion may be better suited (i.e., primarily configured) to heatthe liquid while the other portion is better suited to ignite the fuel.Moreover, a unitary heating and ignition source of consistentconstruction, or any other heating and ignition source, may be disposedwith a first portion in the liquid fuel and a second portion in the fuelvapor. In such a configuration, the portion in the liquid fuel may beconsidered a heating area while the portion in the fuel vapor may beconsidered an ignition area and, in some applications, a heating source.

As discussed above, heating and ignition source 78 may comprise anynumber of devices, structures, circuits, members, and/or materials. Insome embodiments, heating and ignition source 78 may include anelectrical resistance heating element 100. Electrical resistance heatingelement 100 may include a conventional wire made of suitableelectrically resistant materials that generate heat upon receipt of anelectric current. Illustrative, non-exclusive examples of such materialsinclude tungsten and Nichrome alloys (such as 80Ni20Cr and60Ni16Cr24Fe). Additionally, the materials used in electrical resistanceheating element 100 may be selected based on their performance in theconditions of the fuel chamber, such as having a high thermal breakdowntemperature, being non-reactive with the carbon-containing fuels in thefuel chamber, and being otherwise suitable under other conditions thatmay affect the ability of the heating and ignition source to heat andignite the fuel in the fuel chamber. Exemplary materials includesilicon-carbide and other refractory materials. It is within the scopeof the present disclosure that any suitable material or combination ofmaterials may be used in heating and ignition source 78. The particularmaterials used in a given embodiment may depend on such factors as thecarbon-containing feedstock in the fuel stream, the hydrogen-producingmechanism(s) utilized by the fuel processor, the configuration of theheating assembly and fuel chamber, the configuration and disposition ofthe heating and ignition source, etc.

With continued reference to FIG. 12, heating and ignition source 78 isillustrated as being optionally coupled to, and/or in communicationwith, a controller 102 that is adapted to monitor and/or control theoperation and/or operating state of the heating and ignition source.Controller 102 may be any suitable manual or automated controlleradapted to do at least one of turning the heating and ignition source onand off, controlling the rate of heating of heating and ignition source78, and controlling its surface temperature over time, among otherpossible functions. Controller 102 may be disposed entirely withinheating assembly 60, partially within heating assembly 60 and partiallyoutside of the heating assembly, or completely outside of heatingassembly 60, but in communication with the heating and ignition source.In some embodiments, controller 102 may be outside of heating assembly60 but within fuel processing assembly 10 as illustrated in FIG. 12. Itis also within the scope of the present disclosure that controller 102may be disposed outside of the fuel processing assembly for moreconvenient user access during operation of the fuel processing assembly.In some embodiments, controller 102 may include, and/or be incommunication with, a power source 103 for the heating and ignitionsource (such as to regulate the delivery of power therefrom). Thecontroller may be adapted to perform other functions, and accordingly,controller 102 may be implemented as a portion, or functional component,of a controller for the fuel processing assembly and/or fuel cell systemwithin which the heating assembly is utilized.

As discussed, heating assembly 60 (and/or burner assembly 62) mayinclude a primary burner assembly 58 in addition to start-up burnerassembly 56. In FIG. 12, a primary burner assembly 58 is schematicallyillustrated and may be adapted to receive a gaseous fuel stream. Forexample, byproduct stream 28 may be delivered to the heating assemblyfor use as a fuel for the primary burner assembly. As discussed in moredetail herein, the primary burner assembly, when present, may bepositioned in a variety of orientations relative to the start-up burnerassembly. These illustrative positions include, but are not limited to,positions in which the primary burner assembly is recessed within thestart-up burner assembly, positions in which the primary burner assemblyis positioned above (i.e., closer to the hydrogen-producing region) thestart-up burner assembly, and positions in which the primary burnerassembly and the start-up burner assembly are positioned at the same, orsimilar, distances relative to the hydrogen-producing region. Althoughillustrated in the example shown in FIG. 12, it is also within the scopeof the present disclosure that the byproduct stream is not delivered tothe heating assembly, that another gaseous fuel stream is delivered tothe primary burner assembly, that the heating assembly does not includea primary burner assembly, and/or that the byproduct (and/or othergaseous fuel stream) is delivered to the start-up burner assembly forcombustion during hydrogen-producing operation of the fuel processingassembly.

FIG. 14 illustrates another example of a fuel processing assembly 10that includes a fuel processor 12, hydrogen-producing region 19, andheating assembly 60 substantially as described above, with thesecomponents being identified with consistent reference numerals asdiscussed previously. It is within the scope of the present disclosurethat any of the structures, elements and/or variants discussed and/orillustrated herein may be used with or in these components and fuelprocessing assembly 10. As illustrated, FIG. 14 provides another exampleof a heating assembly 60 that includes a start-up burner assembly 56 anda main burner assembly 58. Heating assembly 60 also includes a fuelchamber 76 and a heating and ignition source 78. Fuel chamber 76 isillustrated with a bottom 92, side walls 94, and a top member 104, whichmay be a partial top member, as illustrated, or a full top member asdiscussed above. As illustrated at 105, the top member 104 may, but isnot required to, include one or more vents, or air passages, 105 throughwhich an air stream may be drawn or otherwise enter the ignition, vaporand/or combustion region.

Additionally, fuel chamber 76 may optionally include at least one baffle106, illustrated in dotted lines in FIG. 14, which may cooperate withthe top member to at least partially define, or separate, the fuel vaporregion and/or the ignition region 80 and combustion region 82. Asdiscussed above, ignition region 80 includes the region in which theinitial ignition of the fuel in fuel chamber 76 occurs. Ignition region80 and combustion region 82 may be distinguished by the ignition regionbeing the area in which the fuel vapor is ignited by the heating andignition source and the combustion region being any region in which thefuel is combusted by propagation of the flame from the ignition region.In some embodiments, the ignition region 80 and combustion region 82 maybe separated from each other. One example of such a configuration isillustrated in FIG. 14 with the inclusion of the optional baffle 106 andtop member 104. As illustrated, baffle 106 extends downward from topmember 104 to form an at least partially enclosed ignition chamber 108.Heating and ignition source 78 is disposed within ignition chamber 108and may be disposed in the fuel vapor region therein, the liquid fuelregion therein, or partially in both the liquid fuel region and thevapor fuel region, as discussed above.

Ignition chamber 108 may be configured to at least partially confine thefuel vapor evaporating from the liquid fuel as the heating and ignitionsource heats the fuel chamber. By at least partially confining the fuelvapor, ignition chamber 108 may facilitate or assist in initiatingignition of the (heated) fuel by reducing the dissipation of the fuelvapor and minimizing the possibility that fuel vapor can be blown awayfrom the heating and ignition source by environmental conditions. Thesefactors otherwise could result in an actual ignition temperature orflash point that is above the theoretical ignition temperature or flashpoint of the particular fuel composition. When fuel chamber 76 includesan ignition region 80, such as ignition chamber 108, it is within thescope of the present disclosure that the ignition region may be incommunication with the combustion region such that the flame andcombustion initiated in the ignition region can propagate to thecombustion region. This is illustrated in FIG. 14 by baffle 106terminating above the surface of the liquid fuel region, and therebydefining a flame passage 107 through which the flame and combustion maytravel or propagate out of ignition chamber 108 to the remainder of fuelchamber 76.

With reference to FIGS. 12 and 14, vaporization region 69 is illustratedas a length of tubing 115 that extends generally intermediate, orbetween, heating assembly 60 and hydrogen-producing region 19. In theillustrated example, the vaporization region tubing 115), is configuredto define a plurality of flow paths that extend generally parallel tothe heating assembly and the hydrogen-producing region, therebyproviding a comparatively greater heat transfer effect than if the feedstream merely passed between the heating assembly and thehydrogen-producing region a single time. The illustrated example alsodemonstrates that the tubing extends along a sinusoids or otherlaterally-extending path beneath the hydrogen-producing region, whichalso increases the heat transfer effect (i.e., the amount of time thatthe feed stream is heated by the heated exhaust stream prior to beingdelivered to the hydrogen-producing region. The illustrated example isintended to be just that, an example, as the shape, orientation, length,cross-sectional area, relative position to the hydrogen-producing regionand/or heating assembly, number of paths, etc. of the vaporizationregion may vary without departing from the scope of the presentdisclosure. Regardless of its particular configuration, the regionshould be designed to receive the liquid feed stream that will be usedto produce hydrogen gas in the hydrogen-producing region of the fuelprocessor and to deliver this stream as a vaporized feed stream to thehydrogen-producing region, with the feed stream being vaporized in thevaporization region through heat exchange with at least the exhauststream from the heating assembly.

Heating assemblies 60 according to the present disclosure may be usedwith fuel processing assemblies that do not include a vaporizationregion for the feed stream for the hydrogen-producing (reforming) regionof the fuel processor and/or may include a vaporization region that isnot directly heated by stream 66 and/or which is not positioned betweenthe heating assembly and region 19. When configured with a vaporizationregion that includes at least one length of tubing or other enclosedregion in which the feed stream is vaporized by heat exchange with theheated exhaust stream 66 from the heating assembly flowing external thetubing or other region through which the feed stream flows to bevaporized, tubing/region 115 may be formed or shaped in anyconfiguration designed to provide a desired amount of exposure time, andcoincident heat transfer, in the vaporization region for the feed streamprior to entering the fuel processor.

FIG. 14 also illustrates that fuel chambers 76 according to the presentdisclosure may (but are not required to) include a transport medium 110that is disposed at least substantially in the liquid fuel region offuel chamber 76. Transport medium 110 may be configured to draw theliquid fuel in fuel chamber 76 to the top, or top surface, 112 of thetransport medium for combustion. At least the top surface of thetransport medium, and optionally additional regions of the mediumproximate the top surface, may extend to the surface and/or out of theliquid fuel region. Accordingly, transport medium 110 may include one ormore materials and/or structures adapted to moving (i.e., conveying orotherwise transporting) the liquid fuel from the fuel chamber to thetop, or top surface, 112 of the transport medium. Fire-resistantmaterials and materials adapted to tolerate elevated temperatures andthe particular chemical environment of fuel chamber 76 may be utilized.For example, transport medium 110 may include ceramic or glass materialsin some embodiments. When a solid block or ceramic or other absorbentmaterial is used as transport medium, this material may, but is notrequired to, include a plurality of holes or other apertures that aredrilled or otherwise fanned into the material.

In some embodiments, transport medium 110 may be porous or otherwiseadapted to absorb the liquid fuel in fuel chamber 76. Absorbentmaterials 122 in transport medium 110 may enable the transport medium toprevent spillage of the liquid fuel during transport of a fuelprocessing assembly having a fuel chamber that is not substantiallyclosed, such as a fuel chamber configured as an at least substantiallyopen-topped reservoir. The absorbent materials may draw in the liquidfuel and be adapted to move the liquid fuel to the top 112 as liquidfuel is consumed. When transport medium 110 is adapted to at leasttemporarily absorb the liquid fuel that is delivered to the fuelchamber, the transport medium may also be described as a containmentmedium, in that the liquid fuel that is absorbed by the medium (prior tobeing combusted) is prevented from spilling from the fuel region, suchas if the fuel chamber were suddenly tilted or overturned.

Additionally or alternatively, transport medium 110 may include fibers,tubes or other structures 124 that are adapted to wick, such as bycapillary action, the liquid fuel from the bottom of the fuel chamber tothe top 112 of transport medium 110, as shown more clearly in FIG. 14.In some embodiments, a plurality of glass fibers may be arranged toprovide capillary action to move the liquid fuel to the top of transportmedium 110, although this is but one of many suitable structures formedium 110 within the scope of the present disclosure. Similarly, whenglass or other absorptive and/or wicking and/or capillary fibers,strands, or other structures 124 are used, they may extend in anysuitable orientation, including aligned, woven, and/or randomconfigurations. An illustrative, non-exclusive example of a non-wovenconfiguration is a felt formed from the fibers, or strands. Additionalexamples include transport media in wool, blanket, mat, pad, and sheetform. An example of a transport medium that has proven effective isKoawool™ Cerablanket™ refractory ceramic fiber, although others may beused. Transport medium 110 may also be referred to as a transportstructure, and in some embodiments, a containment structure.

Transport medium 110 may, but is not required to in all embodiments,provide a flame-holding surface in the fuel chamber. For example,transport medium 110 may be configured to provide a flame-holding, orflame-positioning, top surface that is spaced from the fuel processor12, hydrogen-producing region 19, vaporization region 69, or otherportion of fuel processing assembly 10 by a predetermined distance toobtain desired heating properties and thermal communication between theflame of the heating assembly 60 and the remaining components of fuelprocessing assembly 10. One advantage of utilizing transport medium 110is that the flame of the combustion can be maintained at a consistentdistance from the other components throughout the combustion processeven as the liquid fuel is consumed.

As seen in FIG. 15, the top 112 of transport medium 110 may be spacedfrom heating and ignition source 78 by a first distance 114, from topmember 104 by a second distance 116, from vaporization region 69 by athird distance 118, and from hydrogen-producing region 19 by a fourthdistance 120. It is within the scope of the present disclosure that anyor all of the distances 114, 116, 118, 120 and any other spacing betweentransport medium 110 and other components of fuel processing assembly 10may be varied to obtain selected, or desired, thermal communicationbetween the components. It is within the scope of the present disclosurethat distance 114 may be zero, or nearly zero, or even that the heatingand ignition source may extend at least partially into, or otherwisebelow the upper surface of, the transport medium, which may be describedas corresponding to a negative first distance.

FIG. 15 illustrates in dashed lines an example of a vaporization region69 that includes a tube, or conduit, 115 that makes a single passbeneath the hydrogen-producing assembly. Also shown in FIGS. 14 and 15in dashed lines at 67 is an example of a distribution conduit that mayextend within the fuel chamber to deliver the liquid fuel stream withinthe chamber. When the fuel chamber includes a transport medium 110, themedium may include a passage for the distribution conduit, may be formedor otherwise extend around the conduit, and/or may be positioned uponthe conduit, etc.

Turning now to FIG. 16, a cross sectional view of heating assembly 60from FIG. 14 is illustrated showing the top view of the heatingassembly, including start-up burner assembly 56. Also shown in FIG. 16is a primary, or main, burner assembly 58. Primary burner assembly 58 isadapted to heat the hydrogen-producing region of the fuel processingassembly and/or vaporize the feed stream for this region during thehydrogen-producing operating state of the fuel processing assembly. Asdiscussed, main burner assembly 58 may be disposed within heatingassembly 60 in liquid fuel region 96, in the fuel vapor region 98, orpartially in the liquid fuel region and partially in the fuel vaporregion. In embodiments including transport medium 110 and a primaryburner assembly 58, such as illustrated in FIGS. 14 and 16, primaryburner assembly 58 may be disposed at least partially within thetransport medium such that the upper surface of the primary burnerassembly coincides, or is substantially coplanar with, the top 112 oftransport medium 110. In some embodiments, primary burner assembly 58may be configured as a burner tube 126 and may include one or moreorifices and/or narrow slots for discharge and combustion of the gaseousfuel fed to the primary burner assembly 58. In FIG. 16, a plurality oforifices are indicated at 128. In this illustrative, non-exclusiveexample, a plurality of spaced-apart orifices 128 are shown, but othersizes, shapes, numbers and/or configuration of apertures may be usedwithout departing from the scope of the present disclosure. Otherconfigurations and shapes and other discharge and combustion methods arewithin the scope of the present disclosure.

FIG. 17 illustrates an example of a burner assembly 60 that includesboth start-up and primary (or main) burner assemblies 56 and 58, withthe primary burner assembly extending within the liquid fuel region 96of the start-up burner assembly. As shown, the primary burner assemblytakes the form of a burner tube, or conduit, 126 that is adapted toreceive a gaseous fuel stream, which is exhausted through one or moreorifices or other outlets 128 and ignited to generate a heatedcombustion stream for providing heat to at least the hydrogen-producingregion of the fuel processing assembly during the hydrogen-producingoperating state of the fuel processing assembly. As discussed, asuitable fuel stream for the primary burner assembly includes thebyproduct stream 28 from a separation or purification region thatremoves impurities and/or undesirable components from the output, ormixed gas, stream 20 produced by the hydrogen-producing region. In someembodiments, another gaseous fuel is utilized as a combustible fuel forthe primary burner assembly, either alone or in combination withbyproduct stream 28.

FIG. 17 illustrates that it is within the scope of the presentdisclosure for the primary burner assembly to extend within the liquidfuel region of the start-up burner assembly. While this construction isnot required, it enables the flames produced by the burner assemblies toextend at the same or similar heights. As discussed, the relativedistances between the portions of the fuel processing assembly to beheated and the components of the heating assembly may vary within thescope of the present disclosure. In some embodiments, it may bedesirable to have these components relatively closely together so as tonot diminish or otherwise less efficiently utilize the heat value of theheated combustion stream. However, the geometry and construction of thefuel processing assembly may provide structural (i.e., space and size)constraints that impair this optional design objective. By recessing theprimary burner assembly within the fuel region of the start-up burnerassembly (for example, instead of locating it above the liquid fuelregion of the start-up burner assembly), the thickness of the burnerassembly, or perhaps more specifically the distances between the flamesproduced by the start-up and primary burner assemblies and thehydrogen-producing region, may be comparatively reduced. In theillustrated example shown in FIG. 17, the orifices 128 on the primaryburner assembly are positioned above the liquid fuel region of thestart-up burner assembly.

When the fuel chamber includes a transport medium and a primary burnerassembly that extend within the liquid fuel region of the fuel chamber,the medium and burner assembly may be oriented in any suitableconfiguration within this region of the fuel chamber. As illustrative,non-exclusive examples, the transport medium may extend on opposedsides, and optionally beneath, the primary burner assembly, the primaryburner assembly may be received within a recess or other passage in thetransport medium, etc. FIG. 17 also provides a graphical example of afuel chamber that includes more than one distribution conduit 67, withthe conduits being illustrated in dashed lines to represent that theconduits are not required structure.

Another illustrative example of a fuel processing assembly 10 with afuel processor 12 having a heating assembly 60 according to the presentdisclosure is shown in FIGS. 18 and 19. Unless otherwise discussed, theillustrated fuel processing assembly may include any of the components,subcomponents, and/or variants described, illustrated, and/orincorporated herein. Similarly, the newly described elements and/orconfigurations of FIGS. 18 and 19 may be utilized with any of the otherfuel processing assemblies described, illustrated and/or incorporatedherein. FIGS. 18 and 19 provide an example of a heating assembly 60 inwhich the primary burner assembly 58 is positioned above fuel chamber76, which contains the start-up burner assembly 56. The illustratedprimary burner assembly includes a transport medium 110 in the liquidfuel region 96 of the fuel chamber and further includes a distributionconduit 67 that is adapted to deliver the liquid fuel stream within thefuel chamber. Although not required, the illustrated conduit extendsacross at least a substantial portion of the fuel chamber and mayinclude apertures to emit liquid fuel along the length of the conduit,and thereby along the length of the liquid fuel region. FIGS. 18 and 19also provide a graphical example of a heating and ignition source 78that includes a resistive element 100 positioned above a central regionof the fuel chamber.

In the illustrated example, the primary burner assembly 58 includes anelongate conduit that extends at least generally parallel to thehydrogen-producing region and vaporization region of the fuel processor,with the primary burner assembly including apertures 128 through which agaseous fuel stream is emitted and combusted from the primary burnerassembly. In the illustrated example, primary burner assembly 58 isadapted to receive the byproduct stream 28 from assembly 25, whichcontains hydrogen-producing region 19 and at least one purificationregion 24. Although not required, assembly 25 may include a housing 27that includes hydrogen-producing region 19, such as may include a streamor other reforming catalyst. Housing 27 may further contain at least onehydrogen-selective membrane and/or methanation catalyst that is adaptedto separate the mixed gas stream produced in the hydrogen-producingregion into product hydrogen stream 14 and byproduct stream 28. FIG. 18also illustrates schematically that the conduit though which byproductstream 28 flows prior to being consumed as a gaseous fuel for primaryburner assembly 58 may (but is not required to) include at least onefilter 123 and/or at least one restrictive orifice 125 that providesbackpressure to the system and thereby promotes greater separation ofhydrogen gas into the product hydrogen stream.

FIGS. 18 and 19 also illustrate that the fluid conduit that formsvaporization region 69 may include one or more preheating conduits 121through which the liquid feed stream is heated prior to being vaporizedin the vaporization region. Preheating of the liquid feed stream mayreduce the length of the vaporization region and/or the time duringwhich the feed stream needs to be in the vaporization region to bevaporized, and/or the amount of heat that is required to be delivered tothe liquid feed stream in the vaporization region to vaporize thestream. Preheating of the liquid feed stream may also provide morestable, or steady flow of the stream, as some liquid streams may createa surging flow if the stream is quickly vaporized.

Illustrative, non-exclusive methods of using the start-up, andoptionally, main, burner assembly are described with respect to FIG. 20.FIG. 20 is a schematic view of a fuel processing assembly 10 that iscoupled to a fuel cell stack 40. As discussed herein, heating assemblies60 according to the present disclosure may be used to heat thehydrogen-producing regions of a variety of fuel processors. For purposesof illustration, the following discussion will describe a heatingassembly according to the present disclosure being used with a fuelprocessor in the form of a steam reformer that is adapted to receive afeed stream 16 containing a carbon-containing feedstock and water.However, it is within the scope of the disclosure that fuel processor 12may take other forms, including (but not limited to) other fuelprocessors that utilize an endothermic hydrogen-producing reaction, asdiscussed above. An example of a suitable steam reformer isschematically illustrated in FIG. 20 and indicated generally at 130.Reformer 130 includes at least one hydrogen-producing region 19 in theform of a reforming region that includes a steam reforming catalyst 23.In the reforming region, an output stream 20, which may in this contextalso be referred to as a reformate, or mixed gas, stream, is producedfrom the water and carbon-containing feedstock forming feed stream 16.As indicated in dashed lines in FIG. 20, reformer 130 may include aregion 25 that includes both a hydrogen-producing region 19 and at leastone purification region 24, such as may be contained in a common housing27.

As discussed previously, feed stream 16 may be a single streamcontaining both water and a water-soluble carbon-containing feedstock,or it may be two or more streams that collectively contain the water andcarbon-containing feedstock(s) that are consumed in the reformingregion. As shown in dashed lines in FIG. 20, it is within the scope ofthe disclosure that at least the carbon-containing feedstock componentof feed stream 16 may also form a combustible fuel stream 64 that isdelivered to heating assembly 60. It is also within the scope of thedisclosure that the complete feed stream (i.e. water andcarbon-containing feedstock) may be used as the combustible fuel streamfor heating assembly 60. For example, a reforming feed stream maycontain approximately 50-75 vol % methanol (or ethanol or anothersuitable water-miscible carbon-containing), and approximately 25-50 vol% water. An example of a particularly well-suited feed stream contains69 vol % methanol and 31 vol % water. This stream may effectively beused as the feed stream for reformer 130 and the combustible fuel streamfor a heating assembly according to the present disclosure. A benefit ofsuch a construction is that a steam reformer or other fuel processorthat produces hydrogen gas from water and a carbon-containing feedstockdoes not need to include more than a single supply, if the water andwater-soluble liquid carbon-containing feedstock are premixed. If not,then the fuel processing assembly still only requires a water supply anda carbon-containing feedstock supply. In contrast, conventional steamreformers with burner assemblies to heat the reformer require a fuelsupply and associated delivery and monitoring systems for the burnerassembly, and this fuel supply is independent from the fuel supply forthe steam reformer.

As an illustrative example, startup of a fuel processor 12 in the formof a steam reformer is discussed with reference to FIG. 20. Duringstartup of a steam reformer or other fuel processor with heatingassembly 60, at least a portion (if not all) of feed stream 16 isdelivered to the heating assembly as liquid fuel stream 64 andthereafter ignited and combusted with air stream 74, or ambient air, toproduce a heated combustion stream 66 that is used to heat the steamreformer. In some embodiments, a pump, such as a positive displacementpump, may be used and adapted to provide a predetermined volume ofliquid fuel stream 64, which may also be described as a predeterminedquantity of liquid, carbon-containing feedstock, to the fuel chamber ofheating assembly 60. As discussed, the liquid fuel stream is deliveredto the fuel chamber and retained therein as a liquid supply of fuel thatis consumed during at least startup of the fuel processing assembly.Therefore, unlike a heating assembly that consumes the fuel stream as itis delivered thereto, the start-up burner assembly 56 of the presentdisclosure at least temporarily stores a volume of liquid fuel. In someembodiments, fuel stream 64 may be configured to provide a stream ofcarbon-containing feedstock during at least the start up phase and,optionally, during the (hydrogen-producing) operating state of the fuelprocessor.

The fuel stream 64 is delivered to the fuel chamber and is heated by theheating and ignition source to increase the vapor pressure of thecarbon-containing fuel in the fuel vapor region of the start up burnerassembly. The fuel vapor is ignited by the heating and ignition source78 and the combustion of the fuel begins. The heat of combustionadjacent the ignition source will radiate and heat the adjacent liquidfuel to further increase the vapor pressure of the carbon-containingfuel in the fuel chamber, allowing the flame and combustion to propagatethroughout the fuel chamber. The temperature at which the fuel vaporignites is determined by a number of factors, as discussed above. Whenthe temperature in the fuel chamber adjacent the heating and ignitionsource reaches the ignition temperature, the fuel vapor is ignitable. Insome embodiments, the fuel vapor ignites, or is ignited, upon beingheated to the ignition temperature. In other embodiments, the fuel vaporonly ignites when the surface temperature of the heating and ignitionsource reaches the heating element ignition temperature, or thetemperature at which the surface of the heating element is sufficientlyhot to ignite the fuel vapor (such as glowing hot or red hot).

Because the combustion can propagate through the fuel chamber 76,heating and ignition source 78 can be significantly smaller than thesize of the fuel chamber. For example, the heating and ignition sourcemay be a localized heat source. A localized heat source is a heatingelement that is substantially smaller than the fuel chamber. The liquidfuel disposed in the fuel chamber has a top surface having a surfacearea. The localized heat source may be coiled, linear, or otherwiseconfigured as described above and may be disposed above, or partiallyabove, the top surface of the liquid fuel. The localized heat source mayhave a footprint (i.e., occupy a space) corresponding to the surfacearea of liquid fuel corresponding or aligned with the localized heatsource. The footprint of the localized heat source may be substantiallysmaller than the surface area of the liquid fuel in the fuel chamber.For example, the footprint may correspond to only 20% of the surfacearea of the liquid fuel region. In other embodiments, the heating andignition source may be sized to have a footprint corresponding to only10%, 5%, or smaller amounts of the surface area. It is within the scopeof the present disclosure that the heating and ignition source belarger, or correspond with a larger percentage of the liquid fuelsurface area, and that the heating and ignition source may be stillsmaller. The size of heating and ignition source 78 and theconfiguration of fuel chamber 76 (i.e., whether there are baffles, topmembers, disposition of the heating and ignition source, etc.) mayaffect the ignition temperature of the carbon-containing fuel and mayalso affect the heating element ignition temperature. Moreover, the sizeand location of the ignition region and combustion region will bedetermined by the configuration of the heating and ignition source, asdescribed above.

Once combustion is initiated in the stall-up burner assembly 56, thecombustion continues, in some cases aided by the transport medium, atleast until the reformer or other hydrogen-producing region 19 is heatedto a selected, or predetermined, temperature. In embodiments utilizing ametered pump to dispense a predetermined amount of carbon-containingfeedstock into the fuel chamber, the amount of fuel dispensed may becalculated to contain at least enough carbon-containing feedstock toraise the temperature of the hydrogen-producing region 19 to thepredetermined temperature. In some embodiments, the predeterminedtemperature to which the start-up burner assembly is adapted to heat thereformer is greater or less than the operating temperature of thehydrogen-producing region. For example, the selected, or predetermined,temperature to which the start-up burner assembly raises the reformermay be a certain amount above or below the desired operating, orreforming, temperature, such as 25-125° C., 25-75° C., 50-100° C., etc.,less than or greater than the reforming temperature.

In embodiments utilizing a metered pump that delivers a predeterminedquantity of fuel to the start-up burner assembly, the start-up burnerassembly 56 may be configured to combust the fuel until all the fuel iscombusted, at which point the primary burner assembly 58 may be operatedto maintain the operating temperature of the fuel processing assembly.In exothermic fuel processing assemblies, the start-up burner assemblymay be operated to raise the fuel processing assembly to thepredetermined temperature, sufficient to begin operating thehydrogen-producing mechanism, and/or to vaporize or otherwise preheatthe feed stream(s) for the fuel processor. At this point, the exothermicreaction of the hydrogen-producing region may be used to maintain theoperating temperature of the hydrogen-producing region.

In embodiments not utilizing a metered pump to dispense thecarbon-containing fuel stream to fuel chamber 76, fuel stream 64 may bedelivered to start-up burner assembly 56 until the hydrogen-producingregion is heated to a predetermined temperature. In this embodiment, thepredetermined temperature may be still lower than the temperaturediscussed above (i.e., there may be a greater difference between thepredetermined temperature and the reforming temperature). One reason forthis is that the fuel chamber may contain a certain amount of liquidfuel that is yet uncombusted when the fuel stream stops flowing to thestart-up burner assembly, which liquid fuel will be combusted to furtherraise the temperature of the fuel processing assembly 10 even after fuelstream 64 stops flowing to start-up burner assembly 56.

As compared to the embodiment with the metered pump, an embodiment witha continual flow of fuel to the start-up burner assembly may have atleast one additional feature, such as a temperature- or time-based flowcontroller and/or a liquid fuel, ignition chamber separator. Thetemperature- or time-based flow controller may be adapted toautomatically stop, either abruptly or gradually, the flow of fuelstream 64 to the start-up burner assembly 56 when the predeterminedtemperature is reached, such as by measuring the temperature directly orby measuring the time and comparing it to empirical temperature/timetables. It is within the scope of the present disclosure that the flowof fuel stream 64 may also be controlled manually in some embodiments.Additionally, start-up burner assembly 56 may include a liquid fuelignition chamber separator to prevent newly added fuel andcarbon-containing feedstock from cooling the liquid fuel already beingheated by the heating and ignition source.

Also within the scope of the present disclosure are start-up heatingassemblies that utilize a metered pump to provide an initial quantity ofliquid fuel to be heated and ignited and then a continuous feed of fuelstream 64 after ignition and combustion has begun, to ensure continuedcombustion until the predetermined temperature is obtained.

Whether a metered pump and predetermined volume is utilized, acontinuous feed of fuel stream 64 is utilized, or some combination ofthe two, upon heating the hydrogen-producing region to the predeterminedtemperature at which feed stream 16 can be delivered to thehydrogen-producing region 19, the feed stream may be directed to thereforming region and hydrogen production may begin. In embodiments wherea common stream, such as composite stream 90 is used as both feed stream16 and fuel stream 64, the transition between supplying fuel stream 64and supplying feed stream 16 may be instantaneous, gradual, or there maybe a break between supplying fuel stream 64 and supplying feed stream16, such as when a metered pump is used to deliver a predeterminedquantity of fuel to heating assembly 60.

As hydrogen gas is produced in the reforming region of the steamreformer, and then purified in one or more purification regions 24, agaseous byproduct stream 28 may be produced and may be delivered to theheating assembly to be used as a fuel stream by the primary burnerassembly 58. FIG. 20 illustrates the byproduct stream being directed toheating assembly 60, as described. In some applications, such as moststeam reformers in which the carbon-containing feedstock is methanol,the byproduct stream should have sufficient heating value that heatingassembly 60 will not require any additional liquid fuel, such asadditional carbon-containing feedstock from feed stream 16. However,when other carbon-containing feedstocks, and especially hydrocarbons,are used, it may be necessary either to continue to supply the primaryburner assembly with carbon-containing feedstock, such as from feedstream 16 or another source, and/or to use some of the product hydrogenstream as a fuel stream in order to provide sufficient fuel to maintainthe temperature of the reformer.

Illustrative, non-exclusive, examples of descriptions of some heatingassemblies and/or fuel processing assemblies within the scope of thepresent disclosure are presented in the following numbered paragraphs.The following paragraphs are not intended to be an exhaustive set ofdescriptions, and are not intended to define minimum or maximum scopesor required elements of the present disclosure. Instead, they areprovided as illustrative examples of some heating assemblies and/or fuelprocessing assemblies, with other descriptions of broader or narrowerscopes still being within the scope of the present disclosure.

1. A fuel processing assembly, comprising:

-   -   a reforming region adapted to receive at least one feed stream        comprising a carbon-containing feedstock and to produce an        output stream comprising hydrogen gas as a majority component;        and    -   a heating assembly in thermal communication with the reforming        region, wherein the heating assembly comprises at least one fuel        chamber and at least one heating and ignition source;    -   wherein the at least one fuel chamber is adapted to receive at        least one fuel stream at a first temperature, the at least one        fuel stream comprising a liquid, combustible, carbon-containing        fuel having an ignition temperature greater than said first        temperature; and    -   wherein the at least one heating and ignition source is adapted        to heat at least a portion of the fuel chamber to raise the        temperature of at least a portion of the carbon-containing fuel        to a second temperature at least as great as the ignition        temperature and to ignite the carbon-containing fuel.

2. The fuel processing assembly of paragraph 1, wherein the feed streamand the fuel stream each comprise at least one common carbon-containingcomponent.

3. The fuel processing assembly of paragraph 1 or paragraph 2, whereinthe feed stream and the fuel stream each comprise at least 25 vol %water and at least one water-miscible carbon-containing component.

4. The fuel processing assembly of paragraph 3, wherein the feed atleast water-miscible carbon-containing component includes methanol.

5. The fuel processing assembly of paragraph 3, wherein the feed atleast water-miscible carbon-containing component includes ethanol.

6. The fuel processing assembly of any preceding paragraph, wherein atleast a portion of the heating assembly is disposed adjacent to thereforming region.

7. The fuel processing assembly of any preceding paragraph, wherein theheating and ignition source comprises an electrical resistance heatingelement adapted to be heated to a heating element ignition temperatureat which the heating element is adapted to ignite the carbon-containingfuel in the chamber.

8. The fuel processing assembly of paragraph 7, wherein the electricalresistance heating element includes a localized heat source.

9. The fuel processing assembly of any preceding paragraph, wherein thefuel chamber includes an at least substantially open reservoir.

10. The fuel processing assembly of any preceding paragraph, wherein theheating assembly further comprises a transport medium disposed in thefuel chamber.

11. The fuel processing assembly of paragraph 10, wherein the transportmedium is adapted to at least temporarily absorb the liquid combustiblecarbon-containing fuel.

12. The fuel processing assembly of paragraph 10 or 11, wherein thetransport medium is adapted to define a flame-holding surface for thefuel.

13. The fuel processing assembly of paragraph 12, wherein the transportmedium is adapted to draw liquid combustible carbon-containing fuel froma liquid fuel region of the fuel chamber to the flame-holding surface.

14. The fuel processing assembly of any preceding paragraph, wherein thefuel chamber includes a liquid fuel region and a fuel vapor region, andwherein at least a portion of the heating and ignition source isdisposed in the fuel vapor region.

15. The fuel processing assembly of paragraph 14, wherein the heatingand ignition source is disposed above the liquid fuel region and betweenthe liquid fuel region and the reforming region.

16. The fuel processing assembly of any preceding paragraph, wherein thefuel chamber is adapted to receive a predetermined volume of combustiblecarbon-containing fuel.

17. The fuel processing assembly of paragraph 16, wherein thepredetermined volume of combustible carbon-containing fuel comprises atleast enough fuel to heat the reforming region to a predeterminedtemperature.

18. A fuel processing assembly, comprising:

-   -   a reforming region adapted to receive at least one feed stream        comprising a carbon-containing feedstock and to produce an        output stream comprising hydrogen gas as a majority component;        and    -   a heating assembly adapted to heat the reforming region; wherein        the heating assembly comprises at least one fuel chamber and at        least one heating and ignition source; wherein the at least one        fuel chamber includes a liquid fuel region and a fuel vapor        region;    -   wherein the at least one fuel chamber is adapted to receive at        least one fuel stream comprising a liquid, combustible,        carbon-containing fuel having an ignition partial pressure;        wherein the carbon-containing fuel in the chamber has an initial        partial pressure that is less than its ignition partial        pressure; and    -   wherein the at least one heating and ignition source is adapted        to heat at least a portion of the fuel chamber to raise the        partial pressure of the carbon-containing fuel in at least a        portion of the fuel vapor region of the fuel chamber to a second        partial pressure at least as great as the ignition partial        pressure and to ignite the fuel.

19. The fuel processing assembly of paragraph 18, wherein the feedstream and the fuel stream each comprise at least one commoncarbon-containing component.

20. The fuel processing assembly of paragraph 18 or paragraph 19,wherein the feed stream and the fuel stream each comprise at least 25vol % water and at least one water-miscible carbon-containing component.

21. The fuel processing assembly of paragraph 20, wherein the feed atleast water-miscible carbon-containing component includes methanol.

22. The fuel processing assembly of paragraph 20, wherein the feed atleast water-miscible carbon-containing component includes ethanol.

23. The fuel processing assembly of any one of paragraphs 18-22, whereinthe at least one heating and ignition source comprises an electricalresistance heating element adapted to be heated to a heating elementignition temperature at which the heating element is adapted to ignitethe carbon-containing fuel in the chamber.

24. The fuel processing assembly of paragraph 23, wherein the electricalresistance heating element includes a localized heat source.

25. The fuel processing assembly of any one of paragraphs 15-24, whereinthe fuel chamber includes an at least substantially open reservoir.

26. The fuel processing assembly of any one of paragraphs 18-25, whereinthe heating assembly further comprises a transport medium disposed inthe fuel chamber.

27. The fuel processing assembly of paragraph 26, wherein the transportmedium is adapted to at least temporarily absorb the liquid combustiblecarbon-containing fuel.

28. The fuel processing assembly of paragraph 26 or 27, wherein thetransport medium is adapted to define a flame-holding surface for thefuel.

29. The fuel processing assembly of paragraph 28, wherein the transportmedium is adapted to draw liquid combustible carbon-containing fuel froma liquid fuel region of the fuel chamber to the flame-holding surface.

30. The fuel processing assembly of any one of paragraphs 18-29, whereinat least a portion of the heating and ignition source is disposed in thefuel vapor region.

31. The fuel processing assembly of any one of paragraphs 30, whereinthe heating and ignition source is disposed above the liquid fuel regionand between the liquid fuel region and the reforming region.

32. The fuel processing assembly of any one of paragraphs 18-31, whereinthe fuel chamber is adapted to receive a predetermined volume ofcombustible carbon-containing fuel.

33. The fuel processing assembly of paragraph 32, wherein thepredetermined volume of combustible carbon-containing fuel comprises atleast enough combustible carbon-containing fuel to heat the reformingregion to a predetermined temperature.

34. In a fuel processing assembly having a reforming region having aminimum hydrogen-production temperature and adapted to receive at leastone feed stream comprising at least a carbon-containing feedstock and toproduce an output stream comprising hydrogen gas as a majoritycomponent, a method of starting up the fuel processing assembly, themethod comprising:

-   -   delivering at least one fuel stream comprising a liquid,        combustible, carbon-containing fuel to a heating assembly at a        first temperature, wherein the carbon-containing fuel has an        ignition temperature greater than the first temperature;    -   heating said fuel stream in the heating assembly with at least        one heating and ignition source to a second temperature at least        as great as the ignition temperature;    -   igniting said fuel stream in the heating assembly with the at        least one heating and ignition source to produce a hot        combustion stream;    -   heating the reforming region of the fuel processing assembly        with the hot combustion stream to a predetermined temperature        related to the minimum hydrogen-production temperature of the        reforming region; and    -   delivering the feed stream containing at least a        carbon-containing feedstock to the reforming region to produce        the output stream.

35. The method of paragraph 34, wherein the feed stream and the fuelstream each comprise at least one common carbon-containing componentdelivered from a common supply source.

36 The method of paragraph 34 or paragraph 35, wherein the feed streamand the fuel stream each comprise at least 25 vol % water and at leastone water-miscible carbon-containing component.

37 The method of paragraph 36, wherein the feed at least water-misciblecarbon-containing component includes methanol.

38. The method of paragraph 36, wherein the feed at least water-misciblecarbon-containing component includes ethanol.

39. The method of any one of paragraphs 34-38, wherein the at least oneheating and ignition source comprises an electrical resistance heatingelement; and wherein igniting the fuel stream in the heating assemblyincludes heating the electrical resistance heating element to a heatingelement ignition temperature at which the heating element is adapted toignite the carbon-containing fuel in the heating assembly.

40. The method of any one of paragraphs 34-39, wherein the heatingassembly includes a fuel chamber having a liquid fuel region and a fuelvapor region, wherein the carbon-containing fuel delivered to the fuelchamber has a first partial pressure, and wherein the carbon-containingfuel has an ignition partial pressure greater than the first partialpressure, wherein heating the fuel stream in the heating assemblyincludes heating at least a portion of the carbon-containing fuel in theliquid fuel region to increase at least one of the temperature and thepartial pressure of the carbon-containing fuel in at least a portion ofthe fuel vapor region to a second temperature and a second partialpressure at least as great as the ignition temperature or ignitionpartial pressure.

41. The method of any one of paragraphs 34-40, wherein delivering a fuelstream to the heating assembly includes delivering a predeterminedvolume of combustible carbon-containing fuel.

42. The method of any one of paragraphs 34-41, wherein the heatingassembly includes a fuel chamber having a liquid fuel region and a fuelvapor region; wherein a transport medium is disposed at least in theliquid fuel region; wherein igniting the fuel stream in the heatingassembly includes creating a flame at an interface between the liquidfuel region and the fuel vapor region; and wherein heating the reformingregion with the heated stream includes wicking the liquidcarbon-containing fuel through the transport medium to the interfacebetween the liquid fuel region and the fuel vapor region.

43. The use of any of the fuel processing assemblies of paragraphs 1-42.

INDUSTRIAL APPLICABILITY

Heating assemblies, steam reformers, fuel processing assemblies, andfuel cell systems according to the present disclosure are applicable tothe fuel processing, fuel cell and other industries in which hydrogengas is produced, and in the case of fuel cell systems, consumed by afuel cell stack to produce an electric current.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. Similarly, where theclaims recite “a” or “a first” element or the equivalent thereof, suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower, or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. In a fuel processing assembly having a reforming region having aminimum hydrogen-production temperature and adapted to receive at leastone feed stream comprising at least a carbon-containing feedstock and toproduce an output stream comprising hydrogen gas as a majoritycomponent, a method of starting up the fuel processing assembly, themethod comprising: delivering at least one fuel stream comprising aliquid, combustible, carbon-containing fuel to a heating assembly at afirst temperature, wherein the carbon-containing fuel has an ignitiontemperature greater than the first temperature; heating said fuel streamin the heating assembly with at least one heating and ignition source toa second temperature at least as great as the ignition temperature;igniting said fuel stream in the heating assembly with the at least oneheating and ignition source to produce a combustion stream; heating thereforming region of the fuel processing assembly with the combustionstream to a predetermined temperature related to the minimumhydrogen-production temperature of the reforming region; and deliveringthe feed stream containing at least a carbon-containing feedstock to thereforming region to produce the output stream.
 2. The method of claim 1,wherein the feed stream and the fuel stream each comprise at least onecommon carbon-containing component delivered from a common supplysource.
 3. The method of claim 2, wherein the feed stream and the fuelstream each comprise at least 25 vol % water and at least onewater-miscible carbon-containing component.
 4. The method of claim 1,wherein the at least one heating and ignition source comprises anelectrical resistance heating element; and wherein igniting the fuelstream in the heating assembly includes heating the electricalresistance heating element to a heating element ignition temperature atwhich the heating element is adapted to ignite the carbon-containingfuel in the heating assembly.
 5. The method of claim 1, wherein theheating assembly includes a fuel chamber having a liquid fuel region anda fuel vapor region, wherein the carbon-containing fuel delivered to thefuel chamber has a first partial pressure, and wherein thecarbon-containing fuel has an ignition partial pressure greater than thefirst partial pressure, wherein heating the fuel stream in the heatingassembly includes heating at least a portion of the carbon-containingfuel in the liquid fuel region to increase at least one of thetemperature and the partial pressure of the carbon-containing fuel in atleast a portion of the fuel vapor region to a second temperature and asecond partial pressure at least as great as the ignition temperature orignition partial pressure.
 6. The method of claim 1, wherein deliveringa fuel stream to the heating assembly includes delivering apredetermined volume of combustible carbon-containing fuel.
 7. Themethod of claim 1, wherein the heating assembly includes a fuel chamberhaving a liquid fuel region and a fuel vapor region; wherein a transportmedium is disposed at least in the liquid fuel region; wherein ignitingthe fuel stream in the heating assembly includes creating a flame at aninterface between the liquid fuel region and the fuel vapor region; andwherein heating the reforming region with the combustion stream includeswicking the liquid carbon-containing fuel through the transport mediumto the interface between the liquid fuel region and the fuel vaporregion.
 8. The method of claim 1, wherein the heating assembly includesa fuel chamber that includes an at least substantially open top, andwherein the delivering at least one fuel stream includes delivering theat least one fuel stream to the fuel chamber.
 9. The method of claim 8,wherein the delivering at least one fuel stream includes delivering apredetermined volume of combustible carbon-containing fuel, and whereinthe predetermined volume of combustible carbon-containing fuel comprisesat least enough fuel to heat the reforming region to the predeterminedtemperature but not enough fuel to maintain the reforming region at thepredetermined temperature while the reforming region is producing theoutput stream.
 10. The method of claim 3, wherein the at least onewater-miscible carbon-containing component includes methanol.
 11. Themethod of claim 3, wherein the at least one water-misciblecarbon-containing component includes ethanol.
 12. A method of startingup a fuel processing assembly having a reforming region, wherein thereforming region has a minimum hydrogen-production temperature and isadapted to receive at least one feed stream comprising at least acarbon-containing feedstock and to produce therefrom an output streamcomprising hydrogen gas as a majority component, the method comprising:delivering at least one fuel stream comprising a liquid, combustible,carbon-containing fuel to a fuel chamber at a first temperature, whereinthe carbon-containing fuel has an ignition temperature greater than thefirst temperature; retaining a predetermined volume of the liquid,combustible, carbon-containing fuel in the fuel chamber; heating atleast a portion of the fuel chamber to raise the temperature of at leasta portion of fuel vapor formed from and above the liquid, combustible,carbon-containing fuel that is retained in the fuel chamber to a secondtemperature at least as great as the ignition temperature; igniting thefuel vapor formed from and above the liquid, combustible,carbon-containing fuel that is retained in the fuel chamber to produce acombustion stream; heating the reforming region of the fuel processingassembly with the combustion stream to a predetermined temperaturerelated to the minimum hydrogen-production temperature of the reformingregion; and delivering the feed stream containing at least acarbon-containing feedstock to the reforming region to produce theoutput stream.
 13. The method of claim 12, wherein the at least one feedstream and the at least one fuel stream each comprise at least onecommon carbon-containing component.
 14. The method of claim 12, whereinthe at least one feed stream and the at least one fuel stream eachcomprise at least 25 vol % water and at least one water-misciblecarbon-containing component.
 15. The method of claim 14, wherein the atleast one water-miscible carbon-containing component includes methanol.16. The method of claim 14, wherein the at least one water-misciblecarbon-containing component includes ethanol.
 17. The method of claim12, wherein the heating and the igniting are performed by a heating andignition source that comprises an electrical resistance heating elementadapted to be heated to a heating element ignition temperature at whichthe heating element ignites the fuel vapor formed from and above theliquid, combustible, carbon-containing fuel that is retained in the fuelchamber.
 18. The method of claim 17, wherein the electrical resistanceheating element includes a localized heat source.
 19. The method ofclaim 12, wherein a transport medium is disposed in the fuel chamber,and wherein the transport medium defines a flame-holding surface for theliquid, combustible, carbon-containing fuel that is retained in the fuelchamber.
 20. The method of claim 12, wherein the heating and theigniting are performed by a heating ignition source, and wherein atleast a portion of the heating and ignition source is disposed above theliquid, combustible, carbon-containing fuel that is retained in the fuelchamber.
 21. The method of claim 20, wherein the heating and ignitionsource is disposed between the liquid, combustible, carbon-containingfuel that is retained in the fuel chamber and the reforming region. 22.The method of claim 12, wherein the predetermined volume of the liquid,combustible, carbon-containing fuel that is retained in the fuel chambercomprises at least enough fuel to heat the reforming region to thepredetermined temperature but not enough fuel to maintain the reformingregion at the predetermined temperature while the reforming region isproducing the output stream.
 23. The method of claim 12, wherein thefuel chamber includes an at least substantially open top.
 24. A methodof starting up a fuel processing assembly having a reforming region,wherein the reforming region has a minimum hydrogen-productiontemperature and is adapted to receive at least one feed streamcomprising at least a carbon-containing feedstock and to producetherefrom an output stream comprising hydrogen gas as a majoritycomponent, the method comprising: delivering at least one fuel streamcomprising a liquid, combustible, carbon-containing fuel to a fuelchamber, wherein the liquid, combustible, carbon-containing fuel has anignition partial pressure; retaining a predetermined volume of theliquid, combustible, carbon-containing fuel in the fuel chamber, whereinthe ignition partial pressure is greater than an initial partialpressure of fuel vapor formed from and above the liquid, combustible,carbon-containing fuel that is retained in the fuel chamber; heating atleast a portion of the fuel chamber to raise the partial pressure of atleast a portion of the fuel vapor formed from and above the liquid,combustible, carbon-containing fuel that is retained in the fuel chamberto a second partial pressure at least as great as the ignition partialpressure; igniting the fuel vapor formed from and above the liquid,combustible, carbon-containing fuel that is retained in the fuel chamberto produce a combustion stream; heating the reforming region of the fuelprocessing assembly with the combustion stream to a predeterminedtemperature related to the minimum hydrogen-production temperature ofthe reforming region; and delivering the feed stream containing at leasta carbon-containing feedstock to the reforming region to produce theoutput stream.